Did not plan to work on git-annex today..

Unexpectedly ended up making the webapp support HTTPS. Not by default, but if a key and certificate are provided, it'll use them. Great for using the webapp remotely! See the new tip: remote webapp setup.

Also removed support for --listen with a port, which was buggy and not necessary with HTTPS.

Also fixed several webapp/assistant bugs, including one that let it be run in a bare git repository.

And, made the quvi version be probed at runtime, rather than compile time.