*Motivation*

Bump the development version to 2.6.0-SNAPSHOT

*Motivation*

Include the example yaml files in the io distribution package

*Motivation*

Currently all io connectors lack example yaml files. Manually write those files is error-prone.
We need a programmable way that automatically generate example connector yaml files.

*Changes*

- introduce annotations for documenting connector yaml files.
- provide a generator to generate yaml files
- provide a shell script to run generator
- when building io package, generate yaml configs

*Motivation*

We shipped two distributions : server & io-connectors. For people who
run pulsar in docker, we need to put all the built-in connectors into
the docker, so that all built-in connectors are available to be used.

*Solution*

Introduce a `pulsar-all` image to include built-in connectors.

Named it as `pulsar-all` to allow include more pluggable components later, for example, offloaders.

### Motivation

We need to package Pulsar IO connectors as part of the release. 
We provide a new file `apache-pulsar-io-connectors-$VERSION-bin.tar.gz` that contains [NAR](https://medium.com/hashmapinc/nifi-nar-files-explained-14113f7796fd).

In subsequent PR, I'll add the logic to load and use these archives.

Signed-off-by: NSijie Guo <sijie@apache.org>

Remove pulsar-common dependency from pulsar-io-core module and cleanup pulsar-common dependency references (#2020)

*Motivation*

With pulsar-common shading in pulsar-client, conflicts observed when using pulsar-client with connectors. Because pulsar-client shades its dependencies,
while pulsar-io implementations pull in pulsar-common which depends on non-shaded dependencies.

*Changes*

- Move KeyValue class to pulsar-io-core, since all pulsar-io is using it.
- Remove pulsar-common from all pulsar-io implementation modules
- Cleanup all direct usage of pulsar-common when pulsar-client-original is in the place.

* begin renaming process

* more class and directory renames

* move Record classes into pulsar-io

* apply rename to Maven configs

* rename java imports

* update versions in maven configs

* add missing imports

* remove Message class from pulsar-io

* add missing import

* add Reflections util import

* add Utils import

* add missing Record import

* supply missing Record imports

* Added Kafka Source and Kafka Sink to Pulsar Connect

* Standardize on kafka versions for compat and connect

* Added Cassandra Sink Connector

* Added Pulsar Connect interfaces that define connectors that push data into pulsar and take data from pulsar

* Added Twitter connector

* Added hbc core version mapping

* Addressed comments

* Fixed build

* Fixed license header

- Remove function-composition

* Relocate instance and spawner to be under `runtime` package
* fix the pom files and travis build

* Split functions module into api/runtime/api-examples

* Move `org.apache.pulsar.functions.api` package from runtime to api package

* Updates headers with ASF source files header

* change license to additional files