WIP: splits instantiations of several classes accross multiple files

fixes: #474 fixes: #503 (closed)

Similarly as many of you, I suffer long CUDA compilation times, here I try to implement the suggestion exposed in the issue #474.

This MR is more of an experiment of what could be done to decrease the compilation times by spiting instantiation of templates across multiple files. This does it in its maximum extreme which is one instantiation per file. It might not be feasible to have this since it obscure the project structure.

Signed-off-by: Vicente Adolfo Bolea Sanchez vicente.bolea@kitware.com