Fix add-item links for business objects and system/process

* added join_object_id and join_object_type support for ModalSelector
Use `RefreshQueue` to optimize tree branch loading
Remove widget-height optimization until it's optimized
Merge pull request #117 from reciprocity/feature/tree-add-items

A few optimizations and fix a couple cases of tree-item-add
Ensure context.id is cast to an integer
Make sure that permissions in session are always up to date. Fix test
that was failing due to new uniqueness constraint enforcement.
Timestamp of most recent role modification must be placed outside of the
permissions dictionary. Permissions dictionary is currently serialized
to json and passed to the client, and serialization of the Datetime
object fails.