`fs rename` command for modifying template values

When the FS template is changed (for example to make use of the new features in https://github.com/openmicroscopy/openmicroscopy/pull/2701), sysadmins may want to rearrange their old data to match the new template. The `bin/omero fs rename Fileset:ID` command now does that.

Testing as a regular user:
 * bin/omero import something
 * bin/omero fs sets # should list the latest fileset
 * bin/omero fs rename FILESET_ID # should rename it
 * you will be asked to move the files (e.g. as `inplace_user`) outside of OMERO.

Testing as admin:
 * as above, but the bin/omero fs rename step should use the user's name and not root's.
 * If `--move` is passed, then the files should be moved "server-side" with no user interaction.
Missing `from omero import CmdError`.
I will try to flake8 the remaining integration tests in between RCs.