[#96] Refactored EaglePlanBufferProvider to support Providers and Values
[#96] Huge refactoring to remove the need to create providers for every literal in expression.
[#96] Operator unit tests
[#96] Special zero cases for operator unit tests
[#96] Unit tests for core
[#96] Unit tests for DB
[#96] Docs
[#96] Fixed memory leaks
fixes #96