Support more concurrent connections for PHP services

My logs were showing lots of: 
[04-Sep-2014 15:52:41] WARNING: [pool www] server reached pm.max_children setting (5), consider raising it

fixes #175 (hopefully)

fix permissions for owncloud-unlockadmin script

split CardDAV instrctions into a new page and add CalDAV instructions; create nice redirects at /cloud/calendar and /cloud/contacts

Also updating the values for secondary DNS, but we're not set up
for secondary DNS so it won't matter.

see #172

The user might acquire the sources via some means other than a git clone. On Vagrant, the files come in via Vagrant. So test for git before running `git describe`.

Merge branch 'master' of github.com:jkaberg/mailinabox

this will always download the latest ownCloud and upgrade if ownCloud install dir exist, this apphroach allows us to keep existing user plugins. currently not checking if currently installed version is equal to the one we're downloading as I couldn't find a proper solution for that

Add a helper script to unlock ownClouds admin features

locale-safe check if we have enough memory installed

expose the control panel only on PRIMARY_HOSTNAME since /admin might conflict with other stuff hosted on other domains

show the tag or commit the user is on in the output to aid debugging when a user posts the output somewhere

CLI usage for aliases with multiple recipients

reads from /dev/random need to use count= to actually get that many bytes or else reads might be shorter

Also swith blocksize and count at the owncloud-specific key generation to ensure get as much bytes as you wanted.

Switch blocksize and count when reading from urandom with dd, to prevent getting fewer bytes for the secret key.

Fix typo in dns_update.py.

Replace spaces by tabs in 106-109. See 92c7815d.

Allow users to insert custom nginx configuration directives through new optional files.