make who-pushed more efficient...
- add (commented out) values to LOG_DEST in the default rc file to allow
'repo-log' as a destination
- make gl_log() respect this and append update log records to a file called
'gl-log' within the bare repo dir. (This is only the update log records,
not everything.)
- let 'who-pushed' use gl-log if found, and the normal ones (much slower)
only if not
- add more help to who-pushed
- help admin migrate log records (or rather, generate the new ones from the
normal gitolite logs)