Have exome view transition properly

Had to guard near origin, locationScale wasn't being set properly
Refactoring of ReferenceFrame and ExomeReferenceFrame

Trying to reduce duplicate code, make sure we calculate zooms properly for each.
Add getMaxCoordinate and override it in ExomeReferenceFrame

ExomeReferenceFrame takes most arguments in genome coordinates, and we had getChromosomeLength return exome coordinates because it is typically used for scaling. getMaxCoordinate will inform what the maximum allowable input coordinate is for a ReferenceFrame
Merge remote-tracking branch: upstream/master