Static web hosting, instructions weren't rendered

fixes Roundcube getting stuck for some people, hopefully fixes #693

Instructions on how to create a web site for a domain weren't rendered. Users would miss the step about manually creating the directory to put files in there and wouldn't see anything happen

install roundcube from our own mirror, hosted in Josh's AWS S3 account, because sourceforge is down all the time

fixes #750, see #701, see #370

Fix creation of custom MX records.

Add a preflight check for supported architecture

Add a swap file to the system if system memory is less than 2GB, 5GB of free disk space is available, and if no swap file yet exists

Never allow admin panel to be inside a frame, use both modern and old headers. Also set no content sniffing

Add a preflight check for ~/.wgetrc

Fix for putty (Windows) Line Drawing characters to be shown correctly.

ownCloud moved their source code to a new location, breaking our installation script.

Fixes #741.

Create a temporary multiprocessing pool

Add check to preflight for exec on tmp

Allow files in /home/user-data/mail/mailboxes