to avoid reverse dependency libcoreblas->libchameleon
set_coreblas_gemm3m_enabled()/get_coreblas_gemm3m_enabled() allow to set/get
this variable.

Fix a large bunch of warnings, and there are still mistakes that should be fixed before the SC release

change the way we include our own header files --> relative to the root - when plasma is in the same env, chameleon can take some headers not belonging to it (ex: #include descriptor.h, this file states in plasma install dir also) which make compilation errors

change installation directories for headers, executables and docs. Make it relative to chameleon to avoid a bloody mess in system dirs

change copyright - correct whitespace - place cmake module depending on chameleon in cmake_modules and no more in cmake_modules/morse