Sqlite-rx

This is a maintenance release. PFB the updates

- Online backup functionality. This feature was suggested by marekyggdrasil
- Python's multiprocessing module is replaced with billiard
- This is mainly changed to support the backup daemon thread to be started in the server process without any pickling issues.
- Starting this release, documentation can be accessed at https://aosingh.github.io/sqlite_rx/
- Build pipeline is moved to Github actions.
- ContextManager support for SQLiteClient.

This is a maintenance release. PFB the changes

1. `lastrowdid` is included in the query response if available
2. `rowcount` is included in the query response if available
3. In the response `JSON`, the key `row_count` is changed to `rowcount` to be inline with SQLite terminology
4. Removed list comprehension when generating a resultset. Now, we use the `list` callable
5. Minor code formatting changes for better readability
6. Added `Windows OS` in the build matrix
7. Added `Python3.9` in the build matrix

- unittests
- Fixed test coverage report of the server process
- Pytest fixtures for better-organized test cases

- SQLiteServer
- Cleanup logic is included in server.run() method.

- SQLiteClient
- Fixed a bug in the retry logic. Send request again before polling the REQ socket
- Raises an exception when Server is offline

- SQLiteRxError (Base Class)

- SQLiteRxAuthConfigError
- SQLiteRxZAPSetupError
- SQLiteRxTransportError
- SQLiteRxSerializationError
- SQLiteRxCompressionError
- SQLiteRxConnectionError

Build Process tests for 2 additional python platforms
- Python 3. 6
- PyPy3

Fix
- Issue 2

- Docker Support
- CLI script for SQLiteServer
- Removed Logger settings which were defined at the module level. The main driver scripts should setup the logger once.

Docker Support
CLI script for SQLiteServer
Removed Logger settings which were defined at the module level. The main driver scripts should setup the logger once.