* Add IGpioController.

This allows compositing gpio extenders/multiplexers or any other providers with device drivers.

* Hack to get command line build working

* Address feedback, fix the rest of the projects

* Add a few tests, tweak the projects to play nicer with VS

* Rejigger the abstraction in Mcp23xxx

Change the abstraction some and update the tests to map closer to the implementations. Fix a bug in setting single pin values.

* Change PinValue to struct

Allows easier interop with raw data and enables us to extend with additional functionality. This will avoid having to add additional APIs for convenience and repeated typing of `PinValue == PinValue.High ? 1 :  0`.

Doesn't impact existing enum usage.

Sample usage:

``` C#
    class Program
    {
        static void Main(string[] args)
        {
            PinValue value = true;
            Console.WriteLine($"True is {value}");
            TestApi(0);
            Console.WriteLine($"Equality is {PinValue.High == true}");
        }

        public static void TestApi(PinValue value)
        {
            Console.WriteLine($"PinValue is {value}");
        }
    }
```

* Ok, so you can't switch a struct. :) Bonus now that you don't have to. There is no such thing as an invalid PinValue anymore.

Get HD44780 fully working

* Added DS3231 binding

* fixed first and second reviews

* add enum Register and some notes

* Added ADXL345 binding

* Update README.md

* add Acceleration.cs notes

* Update Adxl345.csproj

* fixed first review

* Update GravityRange.cs

* fixed second review

* update .csproj

* Update Adxl345.cs

* add some notes

* add enum Register and some notes

* update README

* Update Adxl345.cs

* Added ADS1115 binding

* fixed first review

* Update Ads1115.cs

* add enum Register and some notes

* fixed second review

* update datasheet link

Moved the 8 bit specific API entry point up to the base class. Did this to allow dropping 16 bit chips into code written for the 8 bit chips without having to recompile. Note that the GPIO style members on the API are agnostic and simply check to see if the pin numbers requested are in range.

Factored the reset api the same way as the write/read api (ie port specificaion is only available on 16 bit chips).

Finished updating the sample program. Removed one sample that we don't support directly (raw writes to register numbers). This is supported through the lower level bus drivers or via inheritance (proitected members) if really needed.

Add methods to interface to get/set multiple pins
Add interface for bus controller to allow inheriting by functionality (e.g. bank selection is only available on 16 bit)

Simple caching of the pin state added as a discussion starting point. Perf measurments (from Hd44780 extended sample):

No optimizations - 25358 ms
Send multiple bits - 22233 ms
Cache GPIO state - 5283 ms

To make it work we'd have to add more smarts if state changes where the cache isn't reliable and provide a way to turn caching on/off as it requires being the only user of the device.

* Added pca95x4 binding

* Updated wording

* Removed duplicate check on interrupt pin

* Updated access modifier

* Updated exception message

* Added Pca95x4 to ReadMe

* Removed unneeded items in proj file

* Removed multi-byte read and write methods

* Adding BrickPi3 device

* fixing names for Linux builds

* fixing name of SPIExceptions.cs in csproj file

* fiex typos in README, ,improved code based on GitHub reviews

* remove specific exceptions to use generic ones, adjusted the code accordingly, added SPI bus Id and chip select line

Makes initial backlight state configurable.
Adds simple Lcd1602/2004 classes.
Tidying.

Tested with 16x2 and 20x4 displays with 4 and 8 bit addressing.
Tested with MCP23008 I2C interface (on CrowPi).
All device input working and tested, including custom characters.
Performance tuned for 8 bit direct access (now 3X as fast).
APIs massaged to align with existing .NET terminology (Console, etc.).
Detailed comments added on behavior and performance considerations.

Will follow up with assembly name changes. Also will add a simple LCD1602 and LCD2004 derived class for the most common cases.

* Added HC-SR501 binding

* fixed first review

* fixed second review

* Update Hcsr501.Samples.csproj

* Update Hcsr501.cs

* Fixing two issues with the bindings template

* Fixing tests as well

* Fix input pin bug and added summaries

* Updated access modifier

* Updated exception message

* Add bit validation back

* Removed validation for GetBit

* Update samples to use preview 2 packages

* Renaming files to PascalCase

* ddressing feedback

* Adding link to myget feed

Mark that preview packages have been published to nuget.org

Add install instructions for IoT.Device.Bindings

* Adding Iot.Device.Bindings package

* Adding missing tag

* Initial commit

* Remove tests add GetDistance

* Add sample

* Update sample

* Ref perform both operations at once

* Fix some review

* Update code to resemble krwq

* Clean up the readmes

* Add fritzing diagram

* Add 1kohm resistor

* Fix class docs

* Adding DHTxx support, software PWM and Servomotor

* Fixing feedbacks from last PR

* Correcting code and documentation based on PR feedbacks

* Added a simple implementation for a MAX7219 device

* Add MatrixTextWriter and optimise Max7219 device

* Fixes issues from pull request comments

* Changes for pull request

* More changes for pull request

* refactoring: rename MatrixTextWriter to MatrixGraphics

* Font implementation optimised

* Added editconfig file

* Beginning of cleaning

* Added summaries and sorted

* Added callback summaries

* Fixed ordering and switch/case based on feedback