Deploy properly with Nokia Qt installer's Frameworks on OSX

Pursuant to a "discussion" here:
https://github.com/bitcoin/bitcoin/issues/2015

The patch does three things:
1. Copies Qt frameworks from a well-known location.
2, On my installation "phonon" plugin is called "phonon_backend". Make sure phonon_backend is ignored.
3. env. variable QTDIR is used to find the plugins directory. On my installation the dir is "/Developer/Application/Qt". I decided that instead of hard-coding this path, setting QTDIR before running the script is a more flexible solution.