Disabled MySQL and phpMyAdmin installation by default.

Left on by accident. Oops.
NginX upstream release
Merge remote-tracking branch 'remotes/vladgh/master'
Reworked nxmksite to insert a better phpMyAdmin configuration.
PhpMyAdmin is now installed from source. This avoids some funk wtih Apache when installing from the Debian base repos.
Added Debian 7 to the list of tested distros.
PhpMyAdmin upstream release.
New vhosts now get a public_html directory that is set as the web root.