Add strip_control_chars helper

The helper removes some non-valid html control characters that don't
have equivalent html entities (&#11;-&#31;).
Clean Outlook update notification request payload

Handle non-valid html characters contained in titles and descriptions of
some events that make the request fail.
Properly handle schemas in alembic autogeneration
Show user error in case chairperson removed twice
Added back LHCRRB templates

As some people are still using them for different purposes.