Simplify the command line options in omego

[pwalczysko]

@manics : As discussed during testing of your PR, the options are not very self-explanatory. Hit the problem with
--skipweb has some compulsory parameters and the name always suggested to me rather that the web will be somehow skipped during the omego upgrade. In fact, this means that the web server will not start automatically after download.
There are other rather intricate and longish options which need rationalising.
See #26

[manics]

If no-one objects I'd like to overhaul all the command line args:

• Rename some args to make them more intuitive (as pointed out above)
• Ensure binary options are flags instead of taking a true/false string
• Remove the reading of most environment-variables, I think passing them explicitly on the command line is clearer, especially if it becomes a general admin tool used outside the OME.
• omego.conf file to store default options

[joshmoore]

@manics: in general, 👍. The migration from our own hand-rolled to argparse wasn't nearly as complete as it could/should have been.

[joshmoore]

Re: omego.conf this is likely something that it would be good to do in the framework level and backport to scc and possibly bin/omero.

[sbesson]

No objection to any of the suggestions above. Seconding @joshmoore re omego.conf. I would probably handle the configuration file work in a separate PR.