"Sudo run chain" operation

This new operation has two parameters: the name of the chain to be executed, the principal name under which it has to be executed. It behaves as the current "Run chain" operation under the session of some one else. Ideally, it is visible in the audit log that a sudo feature was used when logging actions executed.

Note: a minor version of this feature would be to have a "Run chain as Root" that would leverage the UnrestrictedSession already existing feature of Nuxeo.