Win32 testing

NEEDS TESTING AND FIXES FOR LINUX! READ CAREFULLY.

First set of changes that make the cmakefiles generate a _almost_ working libospray.dll under windows.
Caveats:
- one last link error in that libospray.dll doesn't find libospray_embree.lib (even though it does get properly generated!?). All sse-avx,avx2 versions of libembree get generated, though, as well as all ispc files.
- makefiles _only_ build the lib itself, not the application(s) (would need glut for that)
- only works with intel compiler right now. make sure to switch solution over to icc once it is (re-)generated by cmake.
- some functions (getSysTime(), getfullpath() commented out, and replaced by thrown exceptions)
- indentation isn't right, plus there's tabs.
- a few #ifdef's are a bit nasty. in part, the ones related to M_PI and id_t
- currently disabled most warnings in platform.h. it would be better if those warnings got fixed, though...
- probably broke some things on linux build (haven't tested yet)