Fixes: diagnostic seeking 3-seconds before loop

Earlier it moves 3 times the sample rate, but since loop stream position is in bytes rather than samples, it usually moved 0.75 seconds before instead (16-bit stereo PCM).
Also, this commit text is longer than the change itself.
Fixes: added OGG to supported formats in track adding dialog

Earlier it was reflected only in WaveStreamFactory and PlaylistManager. I guess that part could use some codeDRYer...
Creep: added "Echoed Backtrack" loop detection algorithm

Also, added and used "Echoes" list property in wave matching processes/queries. Now it's possible to use multiples of loop length candidates in wave matching queries (e.g. wave is being matched not only 4410000 samples away from reference point, but also 8820000), which should work pretty well if the reference wave occurs more than twice. Or something.
Creep: added skipping loop detection

Now if the program gets stuck on a loop for whatever reason (audio file is a tiny bit corrupted, perhaps?), it's possible to advance to the next track. I guess it's something that requires additional investigation... sometime.
Also, updated "About" section to mark the current version.