Added macro for easy test addition

* also renamed the tests directory to test (convention)
Added targets to build and run tests from root

* Also commiting the deleted files from changing the tests directory to
  test
Implements the Back Substitution algorithm (b->x)
Added implementation of main diag. (blocks)

* The blockify method is the one used with MIC, so it's only suited to
  be run in CPU. TODO: port it to GPU
Added some doxygen comments in the blocks header
Adds test for the GPU point method