Add "trusted" capability to OMERO.fs

[jamoore]

Currently to permit scripting it is necessary for an admin to upload a script as an OriginalFile. Trusted files need to be marked so that they are executable. For example,

   ./omero.fs --add /usr/local/path/matlab --trusted

[jmoore]

As discussed during a May 22 call, the most effective solution to this is to use user-mapping so that OS user X's maps to OMERO user X, and unknown OS user unknown to OMERO will not have their files made visible. The OmeroFs process would have to run as root.

For systems where such a mapping doesn't exist, would it make sense to enable "user" directories:

   ./omero.fs --add /var/omero/users/X --mapto X

and any file that gets copied there belongs to user X. The permissions on the directory are then completely up to the sysadmin. OmeroFs will in most cases still need to be run as root.

[cblackburn]

Moved to Future to clear from 4.0. Needs to be rescheduled.

[cblackburn]

Moving to 4.2. However, r5254 allowing single users to be mapped to directories addresses some of this ticket.

[cblackburn]

Josh via email: "Whenever a repository is used for scripting, we
will need this. And in fact, it may be the simplest way of letting
users just drop in a script and have it work."

[jmoore]

As mentioned under #912,...

As a part of #2073 and #2018 (and tangentially #1740) all official scripts are being placed under lib/scripts and accessed via a ScriptRepositoryI instance. This is a clearer and simpler marker of trust, and allows easier adding of scripts by admins.

This functionality may eventually be useful, but more likely it will be necessary to have a ScriptTemplate in OmeroGrid descriptor. Feel free to open if a use case arises.