Small security changes (salting and sha)

These commits add salting to weceem passwords (for security), make the creation of the admin password (during bootstapping) dynamic to allow for (pre-bootstrap) hashing method changes (ie currently only MD5 would work because the admin password is hard coded) and change the default password hashing scheme to sha-512 (including increasing the password data field to match).
I don't know if you're interested in them at all but here they are if you'd like them :-) I was only going to do a pull request for the salting bit (sha-512 is more of a preference thing) but I got out of order, and my git-fu isn't awesome enough :-p

Changes tested, but not too extensively...