Firefox: Add z-index for sidebar

Adjust other z-index values to 50, and give the dashboard 51

COUCHDB-2234
Override breadcrumbs

In documents module the routeObject manages the breadcrumbs via the
leftheader and does not need the fauxton module's event handlers to
automatically manage the breadcrumbs. This adds an override flag so that
the breadcrumbs won't be automatically added.
added ">" delimiter to breadcrumbs

- includes @robertkowalski’s unit test
- I snuck in a minor fix for the login page (HTML+typo fix)
Editor: do not remove id field for docs

COUCHDB-2341
Editor: don't replace custom id attribute with document-id

If we have a document with an id attribute "foo" and _id: "customid"
added from the user and we do a PUT request for an update,
CouchDB will return: {"ok":true, id: "customid", rev: "123"}

The Model will think it has the id "customid" instead of "foo"
Revert "Firefox: Add z-index for sidebar"

This reverts commit fcb7116c5c550b6a3884e6d81c97d981a54ee881.

The commit broke our modal-windows which are located inside the
dashboard.