Merge pull request #1 from mono/develop

Update my personal fork to the latest version of MonoGame.
Fix for ResolveRelativePath stripping drive char

As per issues #3064 and #3041, parsing a file path through the
ResolveRelativePath function was stripping out the drive letter. This
crash was especially prominent for the sound and video loaders.

This fix will strip out the platform-specific path separation character
if it exists and will not try to remove it if it doesn't.
Merge branch 'develop' of https://github.com/lordoaty/MonoGame into relpath
Refactor of ResolveRelativePath() to support nix systems.
Fixed incorrect `notSeparator` on Windows systems.
Generate cleanup and comments.
Added FileHelpers.ForwardSlash and BackwardSlash to makestuff clearer.
Added unit test for FileHelpers.ResolveRelativePath().
Clearer double backslash.
Simplified the test parameters.
Formatted the test cases better.
Added more test cases.
Added double forward slash case.
Merge branch 'testsfix' into relpath
Removed the semicolon trim after talking to original author about it.
Added ./ tests.
Merge pull request #3093 from SickheadGames/relpath

ResolveRelativePath Fixes