Added selection support

Changes made to the tree selection will intelligently cause autotag to
reload

Switching between autotag and thumbnails will no longer cause reload

Hooks in place to manifest selection in autotag

Added 'loading' graphic when calculating autotag view

Selection of an image will now correctly behave as if the parent dataset
is selected
Update right-hand panel on tag change

If an image in the right-hand panel is selected and it is affected by changes (additions or removals) in auto-tag then it is refreshed
Currently unused in auto-tag, but if multiple images are selected and and one of them is changed then the right-panel is also refreshed