autotools: a few cleanups

1. Generate all files as needed and don't package them with source tarball.
     This forces users to rebuild them rather than caching a copy in the source
     tarball. It also means that many files don't have to be listed (duplicated)
     in Makefile.am.

2. Rename the bitcoin-qt.rc file to avoid potential object name clashes.

3. Find windres in configure and use it to build the .rc file for windows.

4. List res files individiaully in Makefile.am to create proper dependencies.
autotools: don't make so many assumptions about sed
autotools: remove bitcoin-qt.pro
autotools: fix gitian timestamp loop

This is a nasty hack, but it seems to do the trick.