Improve ease of installation, enable CI, small RAM reduction

Installation improvements:

• make the bgen library an internal dependency and build with CMake
• refactor use of CMake

Reduce RAM when using large numbers of cores by only instantiating the dXtEEX array on rank 1.

Bump to version 1.0.3 (update GPLEMMA docs, minor bugfix)

Update docs, resolve error when partitioning samples across ranks with invalid samples in data.

Bump to version 1.0.2 (minor fixes)

Improve partitioning of samples across MPI ranks, fix typo in header used in unit tests, improve documentation.

GPLEMMA functionality release

Commandline opts for GPLEMMA exposed. GPLEMMA is a complementary method described in the following paper
https://www.biorxiv.org/content/10.1101/2020.05.18.098459v1

First release of LEMMA

v1.0.0

Clean up misc files