* Initial attempt at flann packaging.
Python2 somehow works. Python3 does not. Still debugging their
obscure setup.py configuration.
* Flann good enough. Python3 broken but close.
Flake8 checks in place. Unsure about CMAKE_BUILD_TYPE and default
spack behavior.
* spack uses RelWithDebInfo as default build type.
* builds py2/3, but direct site-packages install
* prefix working, empty python install dir
* flann package +python installs correctly
* str format {0} instead of {}
* potential doctest fix
* consistency of build env with PythonPackage
* fix python again, test deptype todo, build type
* potentially enable matlab, untested
