Recognize manual URL changes on doc editor page

This ticket lets users manually change the URL on the doc editor page
and have the page automatically load the new doc.

Closes COUCHDB-2490
change Fauxton username variable in testing
Input field in clone doc modal full width

Just a small style fix. There wasn't enough space so the input field
in the modal now spans 100%.
New waitForAttribute nightwatch helper

This test allows us to not just wait for an element, but for an
element attribute containing a certain value. This can be helpful in a
number of scenarios, like when a JS event changes the content of a page
but the DOM structure remains largely the same (e.g. a form).
Rename index.css and require.js with md5 hash

- removes obsolete "cache buster" setting
- replaces hardcoded require.js and index.cs filenames in settings
files with for non-dev build processes with variables.
- release and couchapp_deploy tasks now rename those two files to
include their hashes, and reference them in the generated index.html
file