Error messages are shown on the frontend; a little cleanup to error message handling in general.
Fix to paginated count results.

They got broken in the error handling changes.
Removed the undo add constraint option in the frontend error report since it doesn't always address the error.

It doesn't always address the error since the error could be caused by removing a constraint or changing an existing constraint. Reverting the change that caused the error would require tracking all changes for a proper unto system.
Changed backend to use python hashlib in instead of the sha library.
Possible minor fixes to the facet code.
Facets and event descriptions list disable more button when there is an error.
Facets clear their lists on an error.