Solves the first diagonal using the GPU
Removed Armadillo due to incompatibility.
Added conversion tool for new matrix format.

* Without Armadillo it's easier to load matrices in the "old" C
  plain format, where the first line of the file presents the
  dimensions of the matrix.
* Removed tests and tools from the "all" target.
* Fixed compilation for arma2plain
* Cleaning up for merge
Added kernel to solve the first super-diagonal