GenomeView 922: Shaded read alignment quality and SNP track

There are two new visual features in GenomeView:
1) Short read alignments contain now visual clues to the read alignment quality. Reads with a high mapping quality are colored dark, while reads with low mapping quality will be lighter.

Picture showing shades of mapping quality

2) At the top of the short read track there is now also a SNP track shows the frequency of alternative nucleotides for a position.

3) Major improvements to the visualization of the gene structure track to make it look a lot less clunky.

4) Uniform mouse-functions throughout the visualization tracks.

Further bug fixes included:
2974564 Status bar updates
2969208 SNP threshold
2957908 configurable read-coverage track
2952768 Shift-drag should always select
2950609 right arrow broken
2947910 AA track layout
2947908 DNA line background
2946612 Navigation Feel