Implement conference series permissions

Implement conference series permissions

This adds the concept of an administrator at the conference series
level. An administrator of a series will:
1. Automatically be administrator on all conferences in the series
2. Have access to time based reports for the series
3. Have access to cross-conference email for the series

In passing, update the time based report template to use the newer
styling, and make it possible to resize the graph with drag/drop.

This also changes the list of available conferences in time reports to
be grouped by conference series, and removes the client side filtering
(since it's now much easier to just shift-click an entire series,
which was really the usecase for the previous filter).