Properly pass in username and password to SVN backends.

The code to initialize the SVN backends wasn't passing in the username and
password during construction (instead they were added later). This caused some
workflows to break, especially when using the PySVN backend.

Fixes bug 3303.
Fix "Need more than 1 value to unpack" with ClearCase.

When generating a clearcase diff by hand and uploading it to an existing review
request, it may not have the desired file revision information in the same
format that RBTools uses. In this case, the filenames won't split correctly.

Testing Done: Actively used.

Fixes bug 3305.

Reviewed at https://reviews.reviewboard.org/r/5713/
Fix up and improve RB.ResourceCollection.

RB.ResourceCollection was documenting and supporting the old-style way
of opting in/out of resetting the collection during fetch. Backbone.js
changed how this worked. We now support the modern way, and document it.

The modern way (Backbone.js 1.1+) is to use 'reset' instead of 'remove'.
Resetting is also opt-in in Backbone.js 1.1, though we flip that for
this collection to make it opt-out. We're not currently using
Backbone.js 1.1, but we want to stay close to this semantics to smooth
over the upgrade process.

It's also pretty useful to be able to specify the maximum number of
items to fetch in each batch. Callers could do this by passing
extraQueryData['max-results'], but that was less than ideal. There's now
a maxResults option that can be passed instead.

There's also fixes for the pagination indicators, hasNext and hasPrev,
which could appear as 'undefined' depending on the payload.