Support defining file attribute

The procfs routines went into an endless loop if data is written to the files 'control' and 'view'.
New mount options allow to change the presentation of the files/directories (user id, group id, file attributes, directory attributes). Changing the attributes (read/write/execute) is allowed, but don't have any effect, because it is not fully implemented.
It's all in package cvsfs-1.0.3.