Merge pull request #45 from randallsquared/master

enable roundcube's password-change plugin
make a bash function to use everywhere we apt-get-install (`DEBIAN_FRONTEND=noninteractive apt-get -qq -y `)

ensures the output is quiet
add a bash function ufw_allow which calls 'ufw allow' but hides its totally useless output
installing roundcube from debian would cause update from ubuntu later, now install from Ubuntu debs

We were installing .deb's from Debian. The next apt-get upgrade would cause roundcube to be upgraded.
Maybe that also triggered the installation of apache. Now install roundcube from Ubuntu. So long as
Ubuntu doesn't post an update to roundcube, at least it won't trigger an upgrade on the next
apt-get upgrade. This should also mean we don't need to purge the installation of apache2.

Also try using apt-mark hold to prevent roundcube from being updated, in case that will trigger
dependencies.
move the Dockerfile to the root to allow the working directory of the repo to be pushed inside the image (rather than inside the container getting a fresh mailinabox from github) so changes in the working copy can be tested in Docker quickly / without pushing to github
ssl: there is no need to use -des3 in key generation if we're just going to remove the passphrase

thanks @konklone for discussion