Fix Tool Views order loading/saving

Tool Views order fixes:

1. Order loading/saving now called from Sublime::MainWindow::saveSettings()/loadSettings() methods. Previous version called from Sublime::MainWindowPrivate::aboutToRemoveView() method which leads to some bugs, for example if we start kdevelop without opened views (editor documents), then change order and close app - in such case the order is not saved (since aboutToRemoveView() method is not called).

2. Fixed order applying to layout. If loaded order miss some already existing buttons then previous version removed such buttons from layout and user had a broken UI.

3. Now each area (Code, Debug,...) have its own order settings. Previous version used one "global" setting which leads to buggy behavior in some cases.