Config.pm: add disable_jailsetup knob

Config.pm: add disable_jailsetup knob

It's possible to configure and run Girocco with full fetch and push
support without needing any special root privileges to set it up.

Such an installation will, obviously, only support pushing via https
through Girocco and will never run a Girocco sshd chroot jail.

It's possible that ssh push and fetch access may still be available
via an ssh mechanism outside Girocco's purview, but in such a case
Girocco itself should never set up its own chroot sshd jail area.

Normally this happens automatically simply by running `make install`
as a non-root user.

However, fingers that have been trained to type `sudo make install`
might do so by accident and possibly even while an `sudo -v` condition
is still active.  Such an accident could be tedious to undo (although
it should not cause any data loss).

Provide a new $Girocco::Config::disable_jailsetup option that can
be set to a true value to always prevent the sshd chroot jail setup
part of `make install` from happening no matter how it's run.

This should make those trained to use `sudo make install` somewhat
happier maintaining a non-sshd-chroot-jail Girocco installation.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>