Ext fs irods master

This is the ownCloud/iRODS external file system integration.

The iRODS PHP API provides a php stream wrapper which was used to easily implement this integration.
The API is taken from the development branch at ssh://irodsguest@code.renci.org/gitroot/irodsphp.

@icewind1991 @MTGap @butonic @karlitschek THX
@LukasReschke can you please double check regarding security issues? THX