[CMake] Adding CMAKE_BUILD_TYPE support to ProjectConfig.cmake

[Alexander Neundorf]

On Tuesday 17 December 2013, J Decker wrote:
> which is... build seperately into seperate directories even with makefile.
> 
> If you don't, all sources will not recompile if you change the
> cmake_buidl_type and you'll get partial debug and partial release
> sources.

typically, you get a different set of compile flags, which will cause all 
source files to be recompiled.
At least from that side it should be safe.

Alex