Build&tests improvements

[bcebere]

Changelog

This PR adds the following features:

1. An easier build process - just run "pip install ." and it downloads and builds the depends and the library.
2. CI workflows for linters.
3. CI workflows for tests on the matrix {Ubuntu, MacOS} x Python{3.6, 3.7, 3.8, 3.9}
4. Simplified CMake setup.

[ghost]

All CLA requirements met.

[olsaarik]

Hi! Thank you for all the work you put into improving the build system and CI! I just tried this and it makes installing EVA much more streamlined. We'll review the changes with the team and act on this soon.