Evaluate Display Contexts

Added notes to the sheet for each of the 'Display' contexts, and it looks like all of them are just being used to place blocks, so if the node_is_islandora_object, and 'Node has term with URI' conditions get surfaced for use directly in block visibility settings then all these contexts could be removed in favour of block visibility settings.

Could be worth considering using Block Group module ( https://www.drupal.org/project/blockgroup → ) to organize the block layout. Something like a 'Media viewer' block group to place in the 'Content Above' region, then have the various viewer blocks placed in that group with their own visibility settings to determine which one gets displayed? And another block group could be 'Non-Collection Repository Item Content Blocks', with the 'Citation Select Block' and 'OAI-PMH Item Links' block in that group, with the block visibility being set in one place on the group instead of setting the same visibility settings on each of those blocks.

Link to github PR: https://github.com/Islandora/islandora/pull/1084
And a patch of the changes from that PR: https://patch-diff.githubusercontent.com/raw/Islandora/islandora/pull/10...

Once islandora module PR is merged, this islandora-starter site PR can be updated and reviewed/merged as well to disable all those Display Contexts (or maybe fully remove those Contexts?) in favour of block visibility configs: https://github.com/Islandora-Devops/islandora-starter-site/pull/212