Rework SCMS stack for easier understanding and naming, improve testing makefile Test.mk (was not parallel safe)

Optimize data structures for SCMS and SCMSFP (in each row store only CN-to-VN and VN-to-CN lessages corresponding to active variable nodes in the row)

Reorganize the repository in separate sub-directories. Update Makefile accordingly. Start working on parity matrix generator.

Clean up tests outputs, fix minor imperfections in C sources, add ifndef-endif to header files, fix dec.c for Self-Corrected Min-Sum