Cascade panel renders, but recalculates base aggregates too often.
Pan works slow.
Pan works in pixel-locked step (a little slow)
Power-of-two zoom working (but still has a subsetting/TL only visible issue).
Merge branch 'master' into UI
Merge branch 'master' into UI
Cascade render works, but renders too often and presents too much blank space for transfer.
Misc cleanup and documentation.
Zoom and pan in cascade render much improved.
Documentation.
Fixing visibility error.
Removing un-used method.
Proof-of-concept subset panel (and misc other fixes).
Fixed subset render edge condition problems.  Can experience out-of-memory if zooming in too far.
In-code view-relative/invariant switch in ARSubsetPanel.

Transfer specialization moved out of the renderer to facilitate this switch.
Accessor methods for view-relative