Write SashimiJunctionRenderer

 Very similar to SpliceJunctionRenderer but renders arcs with circles at the top and no flanking regions
Add separate window for sashimi plot
Add gene track selection and isolating drawing junctions for a particular exon. Not all that clean of an implementation
Add a few different rendering options for shape
Make shallow copies of tracks when loading into SashimiPlot.

Decide whether to draw arc above/below based on end position, so still semi-random but repeatable
Add mouse listeners to SashimiPlot window, so we draw only those selected exons and can change rendering style
Add ability to alter maximum depth (rescale arc height)

Add ZoomSliderPanel (weird height right now).
Resize zoom controls
Add drag capability. Many hacks
Render text at arc height; have fixed arc height instead of using depth to calculate.

Thicken stroke for arcs
Add coverage track rendering
Turn selectedExons into a set, allow multi-select

Paint exons as empty with a border when selected. Have gene track expanded by default, since the user needs to select each exon from each isoform
Make Amino acids a bit transparent, so one can still see what's selected

Looks a bit funny because the exons are still drawn behind the amino acids, but it's not terrible.
Add dragging limits to Sashimi plot window based on original view
Have the zoom slider panel dispatch events to reference frame using Guava EventBus
Set zoom limits in SashimiPlot (can't zoom out too far)
Draw text above/below arcs, instead of at midline
Draw above/below alternating, make sure the above/below stays consistent with pan zoom.

Set Snp threshold so coveragetrack doesn't get colored in sashimi plot
Treat all exons as just loci, highlight them similarly. Still only works in expanded mode
Relocate and rescale coverage track to be centered, autoscaled, only half the height of sashimi track