Added feature for limited user for archiving files in docbox

Added a new Feature "File Access for Limited User" in the DocBox Extension. This feature moves the File Table to a different id, so that it can be used by limited users.

Attention: 

When the feature is activated, the content of the file table is moved from the old to the new table. Depending on the no. of files, this can take some time. 

Usually an external archive is used and the table is small, but in case the files are stored internally, it is recommended to this outside of working hours.