Remember window and splitter positions

[Uncommon]

Preserve window position and state:

• [x] Repository window position & size
• [ ] Splitter and tab states
• [ ] Selected commit
• [ ] Selected branch
• [ ] Selected file
• [ ] Prefs window position and tab

[Uncommon]

The restorable state feature has issues outside the automatic workflow

https://stackoverflow.com/questions/42071277/saving-and-restoring-nswindow-state-cant-restore-firstrepsonder