Add a new PXF plugin to provide read and wrtie access to Ignite database via its native REST API.
- Supports partitioning;
- A dedicated Ignite client with REST API enabled is used to access Ignite database;
- Every SELECT or INSERT query splits tuples of data into groups, each of which is sent from (to) Ignite in one response (query). The size of a group is customizable;
- The implemented REST API can be modified (with relatively small changes) and used to connect to any other database (or service) which supports SQL queries via REST, and responds using JSON objects.
Plugin documentation is available at `pxf/pxf-ignite/README.md`.