Make listview pagination actually functional

Since the data is being supplied by the controller, picking which
slice of data should be presented in the list view is also the
controller's responsibility. Therefore, the list view now passes
two parameters to the controller's search() function: currentPage,
and itemsPerPage. The latter is hardcoded for now, but that will
eventually change.
Make "Remove Users" button work in sfadmin

There is now a user_bulkdelete function in the JSON-RPC API. I
couldn't find a corresponding bulk delete operation in Mongo, at
least not one that takes a list of user ids. (There's a "bulk delete
everything that matches this search parameter" function, but that's
not the same.) So the implementation in the model just cycles through
the user IDs and deletes them one at a time. If we find a better way
to bulk delete a set of IDs in Mongo, we can swap out the appropriate
function later on.
Use PHP 5.3 syntax for database setup script

If our deployment server has PHP 5.3 or below, the [] syntax for
arrays won't be available. It's a pretty trivial change to make,
so we might as well make it.