Just a small comment fix in MathHelper class.

also remove farseer dependency.
Merge pull request #1856 from Shqrdx/commentbranch2

Just a small comment fix in MathHelper class.
Update to project template for Windows Phone solutions to use a drawing surface instead of a DrawingSurfaceBackgroundGrid so that either Landscape or Portrait is supported.

At time of commit supporting Both portrait and landscape on the same page is NOT supported, just one or the other.
Merge pull request #1857 from DDReaper/WindowsPhone-Template-fix

Update to project template for Windows Phone
Merge branch 'develop' of https://github.com/mono/MonoGame into develop.PSM