This changes various controllers to use the new EventCollection class
for retrieving events. This class uses a JOIN LATERAL query on
PostgreSQL to retrieve queries in a more efficient way, while falling
back to a simpler / less efficient query for MySQL.

The EventCollection class also includes a limit on the number of events
to display to prevent malicious users from cycling through all events,
as doing so could put a lot of pressure on the database.

JOIN LATERAL is only supported on PostgreSQL starting with version 9.3.0
and as such this optimisation is only used when using PostgreSQL 9.3 or
newer.

To avoid the use of slow queries, remove some deprecated methods and encourage
the use of ProjectFinder to find projects.

`User#starred_projects` doesn't perform any visibility checks. This has
a couple of problems:

1. It assumes a user can always view all of their starred projects in
   perpetuity (project not changed to private, access revoked, etc.).
2. It assumes that we'll only ever allow a user to star a project they
   can view. This is currently the case, but bugs happen.

Add `User#viewable_starred_projects` to filter the starred projects by
those the user either has explicit access to, or are public or
internal. Then use that in all places where we list the user's starred
projects.

Also moved useless helper methods and directly to the
DashboardController.

Fixed other issues based on feedback

They would try to load JSON from a project even though it isn't a single project