remember column widths, windows size, sort and tree form

[mailchuck]

• [ ] tree form perhaps not as that may be a privacy leak. QT has a config interface that abstracts from OS (e.g. on Windows it puts stuff into registry), QSettings
• [x] Layout and state of main window are stored since https://github.com/mailchuck/PyBitmessage/commit/7a0e6488222b4c479c2fa1aca829193007f305db
• [x] Works on Windows and OSX
• [x] it does not work on on Ubuntu (sync necessary for some reason)
• [x] change "Mailchuck Ltd" to "Bitmessage"
• [x] messages tab
• [x] messages list (like the width of "Date")
• [x] subscription tab
• [x] subscription messages list
• [x] chan tab
• [x] chan messages list
• [ ] sort order (it actually does not keep it anyway even if you switch between folders)
• [ ] which was the last active tab
• [x] blacklist column width
• [ ] ~~saving bound to edit instead of quit?~~

[PeterSurda]

I moved saving to before event.accept, and that appears to have fixed Ubuntu.