Improve performance of gitolite triggers

On a small system of 30 repos and users, this is the runtime before:

    $ time gitolite trigger POST_COMPILE
    real    1m7.612s
    user    0m49.530s
    sys     0m4.647s

This is the runtime after:

    $ time gitolite trigger POST_COMPILE
    real    0m1.382s
    user    0m0.633s
    sys     0m0.060s

However, this code should be rewritten more clearly.
Added temporary additional keydir (better solution TODO)
Fixed typo in gitolite models
Rearranged gitolite trigger due to buffers being too large
Revert gitolite trigger user_list iterator
Fixed the gitolite denied condition