Get rid of the git commit hash in the protocol and elsewhere

The requirement for having .git at compilation time is a huge packageability killer, since every imaginable packaging script strips out RCS information early on. As discussed in IRC, this should kill off the whole git hash affair.

The admin interface is supposed to print protocol version instead of git commit hash now. I did not touch anything in contrib/ so some scripts may require updating to accommodate that.

I've screwed up in dht/dhtcore/RouterModule.c on line 392, that won't work 
and I have no idea how to fix that! That's the only compilation blocker remaining.
admin/README.md should be updated after the above issue is resolved.