Make indico cli handle KeyboardInterrupt
Add console prompt for password and email
Move admin manager to Indico CLI
Make with_zodb rollback on Exceptions
Fix indico admin cli not handling invalid avatars
Post-WIP fixes
Better name for room attribute association table
Set alembic version to HEAD when migrating data

Having to call `indico db prepare` during/after a migration which even
creates your tables is just stupid and people tend to forget it.
Handle None values and defaults in GenericCache
Simplify the caching decorator

None is cachable now, so we don't need tha horrible pickle hack anymore