Fix typos
Soft deletion of apps

Apps:
 - Add deleted_at column to Apps table. This is null when the App
   is not deleted, and is set during soft deletion.
 - Ensure that deleted App objects are NOT accessible from the
   Apps API end-point.
 - Implement soft deletion in the App model. This is used by the
   Apps API end-point for recursive deletion of apps.

Other:
 - Fix query.rb to fully support equals comparison on timestamps.
 - Monkey patch Sequel's AssociationDependencies plugin to support
   returning the association dependencies verbatim.

{Stacks, Orgs, Spaces}:
 - Add filter for soft deleted apps

[Finishes #49861301]
Make soft deleted apps recreatable within the same space.
Merge branch 'soft_deletion_apps_finished'

[finishes #49861301]