1. When user specifies only categories and no participants -
** Track all edits made to all pages in that category in the specified time period
** Note: We probably need some sane limits just in case someone adds a huge category
2. When user specifies categories and participants -
** Track all edits made by those participants to pages in those categories in the specified time period
* If there is a wiki specified for an event but no categories are listed for that wiki and no participants are specified then no stats would be generated for that wiki.
* If there is a wiki specified for an event but no categories are listed for that wiki but participants are specified, then the behavior for that wiki remains the same as before - stats for that wiki would be generated from the edits made by the participants during the event on that wiki.