Properly send registrant email to organizer

Even if all emails to the registrant are disabled, the organizer should
still be able to get an email notification.
Init files for events module
Create event model for indexing
DB migration for event indexing
Implement ConferenceIndex
remove unused code and PEP8 refactoring
Adjust code to reflect new index API
Create categories module
Add migration changes for categories index
Rename table events to events_index
Implement CategoryTitleIndex
Adjust code to reflect new categoryTitle index API
Add initialize methods
Remove useless code for Whoosh indexing
Refactor code in index classes
Renaming and changing DB structure
Refactoring by removing __init__ method
Update migration code
Update message and file name for migration
Use different method to order by descenting