Have splice junction info get reloaded when preferences edited

This is so users don't need to restart IGV

IGV-1933
EQTL support updates
Implement dual-loop method for getSummaryScoresForRange

Need to write tests, but believe this should be correct (maybe not efficient)
Add very basic test and test data for CombinedDataSource
Add additional test of CombinedDataSource
Have Segment inherit from BasicScore
Some scratch work on uneven boundaries
Believe we have a working model of CombinedDataSource.

Only supports addition and subtraction right now, should be easy enough to extend. Not hooked into UI.

IGV-1931
Display variants stacked instead of overlapping.

Samples are still overlapping