Initial support for sort order and commands

Support grouping count, distinct, and findAndModify commands. Query sort order and some command options are now included in the emitted key and affect grouping, but are yet used in the UI.

When aggregating profiler data, system collections are now ignored entirely. Queries on the command collection are considered, and will be included in database and collection views.
Use the default error handler
Remove GitHub ribbon from the index view
Remove unnecessary timezone code

Twig is already configured to print dates in the default timezone.
Bump Silex dependency and update composer.lock
Update README links and connection documentation