Add more to the metadocs.
Add more to the metadocs.

Info about the two doc sets, preprocessor defines to hide details,
and hiding preproc macros from the docs

Armada651/OSVR-Core,godbyk/OSVR-Core,d235j/OSVR-Core,OSVR/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,leemichaelRazer/OSVR-Core,d235j/OSVR-Core,feilen/OSVR-Core,d235j/OSVR-Core,godbyk/OSVR-Core,godbyk/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,leemichaelRazer/OSVR-Core,feilen/OSVR-Core,godbyk/OSVR-Core,feilen/OSVR-Core,d235j/OSVR-Core,Armada651/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,leemichaelRazer/OSVR-Core,OSVR/OSVR-Core,feilen/OSVR-Core,OSVR/OSVR-Core,OSVR/OSVR-Core,Armada651/OSVR-Core,d235j/OSVR-Core,Armada651/OSVR-Core,Armada651/OSVR-Core