Rename index.css and require.js with md5 hash

- removes obsolete "cache buster" setting
- replaces hardcoded require.js and index.css 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
I changed my mind: I agree. Making it self-contained trumps the duplication. I'll change it!