added gui shrink button support

[ghost]

This pull implements a button in Pro Mode to shrink back to Lite Mode.
To do this required altering startup so it always passes thru Lite mode before activating Pro Mode, otherwise if started in Qt mode it cannot switch back to Lite.

The Default GUI option chooses which window to show at start: Lite or Pro (Qt).

There is some extra code in gui_qt.py that may possibly be pruned since ElectrumGui is no longer called but this assumes that gui_lite.py has all functionality.

I tested all variations of startup that I could think up. Default Lite, Default Qt, First Use.
It worked fine for me.

My "merged" branch has this feature already merged for anyone who wants to test it.

[maran]

There is a small problem when merging this into mainline master. I've modified the lite GUI so that cfg is assigned as self.cfg so it can be shared throughout the whole module. The if statement on line 256 does not reflect that yet, if you merge master into your local branch it should become apparent when booting.

An other problem is that the command line flag doesn't seem to work anymore. Specifying --gui qt still boots the lite (as setup in the config) in master this functionality still works.

[ghost]

I'd forgotten about the cmd line override. I'll have a look at that again.
Probably it needs to be passed in to ElectrumGui and used instead of cfg (since it originates from cfg during option parsing anyway). We don't want to alter cfg as that would result in permanent change.

On my branch "lite-settings" (for adding menu item for settings) I simplified the MiniWindow and ElectrumWindow call args anyway - so it may be best if we held this one back and I combine these two as they both play with the call args for the windows. My choice was to have ElectrumGui pass it's "self" down so that it is "parent" to both windows. That allows access to almost everything from both Lite and Qt. Then wallet, expand, shrink are all available via parent. cfg could be opened once in ElectrumGui and then also be available to both.

[maran]

Those changes sound like a very good plan. Perhaps close this specific pull request and redefine it based upon the suggestion of passing ElectrumGui down to the specific GUI's.

[ghost]

Will do.