Add namecoin qt

This merges namecoin-qt into master. It merges in the master branch from namecoin-qt/namecoin-qt and the namecoin-qt branch from  namecoin/namecoin.

To build namecoind:

    $ cd src
    $ make USE_UPNP= namecoind

To build namecoin-qt

    $ qmake "USE_UPNP=-"
    $ make