Make it so you can open a pydm display with the nav bar (et al) hidden

[jjanice]

feature request:

From the command line, you can open a pydm display with parameters:

--hide-nav-bar Start PyDM with the navigation bar hidden.
--hide-menu-bar Start PyDM with the menu bar hidden.
--hide-status-bar Start PyDM with the status bar hidden.

It would be nice to have those options within pydm so I could check boxes in designer to hide/show these bars.

Now you can do this with a shell command, but staying within pydm would be nicer.