[FNA] FNA Code Style: Tabbing, etc. - Media Dir

I *think* I've got a handle on the style now, and I've changed my MD formatting
prefs to be more in sync with your guidelines. 

Please tell me your thoughts on the MediaSource[] assignment
(MediaSource.cs, 44).  I split the assignment to multiple lines because of line
length.  I originally put the braces to separate lines (like you do with other
constructs), but with the new object being created inline it makes it a tiny bit
harder to grok that it is an array (IMHO).

If you'd prefer it be like:

MediaSource[] result = 
{ 
        new MediaSource("DumpMediaSource", MediaSourceType.LocalDevice)
};

then I will make that change.
Fixed a one-liner and one long line that I missed
until reviewing on GitHub.
Miscellaneous fixups

Eliminate unused variables in getter/setters, alter array format, add back
SavePicture functions, remove unimplemented Playlist::Songs comment block.
Merge pull request #170 from 3vi1/monogame-sdl2

[FNA] FNA Code Style: Tabbing, etc. - Media Dir