Commit migrated from https://github.com/dotnet/corefx/commit/1f8b5264a8156f91c48b2dc344d5410ee6f574cb

Commit migrated from https://github.com/dotnet/corefx/commit/71de1aac5cf3e5dc87714ae0cc829e1fa98f7c5d

Commit migrated from https://github.com/dotnet/corefx/commit/be08afd9701053f5f9369762db58b87c8ca9559f

Commit migrated from https://github.com/dotnet/corefx/commit/030e29992f6be20ffb9d9d3e799118f3354bce22

This moves all library packages that make up
NETStandard.Library to the open.

I'll follow up with some refactoring of these
to ensure that all packages with NETStandard.Platform
use runtime packages to garuntee that they can
be replaced with an alternate implementation.


Commit migrated from https://github.com/dotnet/corefx/commit/d90273eec38cd189c918cbcd070e3aed4e196201

After this change if you build a .builds file it will all projects
defined in it. However if you specify OSGroup or FilterOSGroup as a property
it will only build the projects that are for that OSGroup or AnyOS.

Change the default OSGroup to AnyOS instead of Windows_NT.

By default if you build from the root it will only filter the projects to
just the OS that you are building on (including anything that is AnyOS).

If you want to build all projects for all OS's from the root pass
/p:BuildAllOSGroups=true property from the command line.

Includes an update to project-guidelines.md and windows-instructions.md docs
with information on the changes.

[MERGE with support commit]


Commit migrated from https://github.com/dotnet/corefx/commit/7146f1be15bbe9b82949cb71b3f1d3548a10fd5e

Adds packages for a few libraries and integrates
package build into the binary build process.


Commit migrated from https://github.com/dotnet/corefx/commit/fa811f379c45504a4b5fdae5b08a22a31202bea9

Commit migrated from https://github.com/dotnet/corefx/commit/5e0e3c58f681f0aa4aa430a5d25d05c82280e20a

Commit migrated from https://github.com/dotnet/corefx/commit/6dcf416a2ca769f35d2cea97e9ce99643696bb4e

Commit migrated from https://github.com/dotnet/corefx/commit/a20fd22b1e44d13e437c235a957a47a2af52838d