Update to SDK 0.5.0.1

[mattebb]

Thought I should send this back for some merging - I've done a fair bit of work on this cleaning it up and rounding out functionality. This is up to date with the v0.5.0.1SDK, which is the latest available version that supports Mac OS X. Would like to get some time to get into 0.6 since there are some interesting new features, but lack of Mac support makes things annoying (boot camp dev environment blah blah...)

Best to look at the commits, but a brief summary:

• Run-time control over HMD capabilities and distortion behaviour
• Dynamic render target size (can increase/decrease resolution at runtime)
• A few small nifty things like retrieving user eye height, dismissing safety warning
• Cleaned up code paths, SDK and Client rendering now more unified