HMD Refactoring + Chrom Aberr changes

Refactoring so that there aren't multiple HMD types, as this could get
unwieldy, particularly as the OVR SDK Provides some of the required info
(such as which HMD is currently in use).
Removed most fx files, replaced with a single one which takes more
params depending on the active HMD
Use chromatic abberation coefficients from the SDK depending on HMD type
Chromatic Abberation can be turned off using SHIFT+C (just in case you
want to see it without)
Fixed some other very minor things (unnecesary logging