Admin and hook improvements

Improve hook installation.
Write, store and housekeep hook logs at `$REPOS/log/`.
Clean options for hook installation.
Install `svnperms.conf` from repository root.
TZ=UTC for all hook scripts.

Improve diagnostics for hooks.
Custom configuations per repositories, not executables.
Configurable `pre-revprop-change` permissions.
Hooks to work best under Subversion 1.8+.
Add modified `svnperms.py` in distribution.
Trac 0.12+ changeset added and modified notification.

Trac URL template.
Trac comment edit permission.

Fix usage of FCM_CONF_PATH for admin.
Improve documentation and logic for admin configuration.

Get user info via LDAP or traditional Unix password file.
Use UUID to generate initial svnserve passwords
fcm-add-svn-repos-and-trac-env: new admin command.
fcm-add-svn-repos: new admin command
fcm-manage-trac-env-session: new admin command

pre-commit: block branch create with bad owner

post-commit-bg: rename repository dump.
post-commit-bg: branch owner notification

post-* hooks: configurable notification `From:` field

Test batteries for hooks, and selected admin utilities.

fcm commit/branch-rm: fix branch owner test to use correct user ID.