Generic data distribution specification

This is a generic implementation of custom data distributions. (Follow-up and close !357 (closed)) Some side-effects:

• A new helper function has been added to the testings to ease the use of this new possibility
• All testings that can use a custom distribution are now able to do it through the --custom=filename.txt option.
• All copies of the matrices that are done in testing are switched to CHAMELEON_MAT_ALLOC_TILE, or directly to mandatory 2dbc format if needed.
• WARNING: For now, the custom distribution is applied to all matrices used in the test. For example in GEMM, it is applied to A, B and C.