Fix FileUtils.isTabDelimited so it matches doc; samples first 5 lines and returns true iff there are at least that many tab delimited columns
Add ability to register loader for file extensions to API

IGV-1882
Load annotation track by loading file with custom extension (just added to IGV API)

Only have "add annotation" context menu entry in MongoFeatureTracks, not all feature tracks

IGV-2020
Move FeatDBObject to its own class, rename

IGV-2020
Load plugins earlier in process (in case of custom file loading)

IGV-1882
Use DBFeature.IGVFeat in MongoFeatureSource/Track, so the object being displayed has a backreference to the DB object

This is so we can edit

IGV-2020
Add name field

Add delete functionality to dialog

IGV-2020
Remove score

Add color, stored as a string in DB

IGV-2020