Fixes to Game startup when using a unit test runner.
The Content.RootDirectory cannot be absolute.
Removed local directory reference.
Using AppDomain.CurrentDomain.BaseDirectory seems to be a more reliable way of getting the working dir.
I was wrong.... Content.RootDirectory can have an absolute path.  MonoGame needs fixing here.
Game takes care of disposing GraphicsDeviceManager.
Fixed keyboard mapping for linux to include the right shift key, the right windows key, and the ? key.
We set the SamplerState even if the texture is null.
Implemented missing SoundEffect.IsDisposed
Merge pull request #1547 from theodis/develop

Fixed missing keyboard mapping for Linux
Merge pull request #1560 from dellis1972/soundeffectdisposed

Implemented missing SoundEffect.IsDisposed
Addition of the MathHelper unit test. More tests are needed.
Merge pull request #1530 from SickheadGames/testfix

Unit Test Fixes
Merge pull request #1562 from totallyeviljake/MATH_HELPER_UNIT_TEST

Addition of the MathHelper unit test. More tests are needed.
Re-orginization of the Test folder.
The tests are now under Framework folder.
The test runner support classes are under the Runner folder.
Merge pull request #1548 from SickheadGames/effectpass

Fix SamplerState in EffectPass
Moved Info.plist to Runner/iOS folder.
Added link to Info.plist.
Merge pull request #1563 from SickheadGames/testfix

Reorginization Of The Test Folder
Revert "AccelerometerAvailable will never return true when running in the simulator. Added check if running on simulator to return true."

This reverts commit 8280e7366aa6e85e5386743502736788976f3672.