WIP: Kill MainWindowPlugin
Kill MainWindow
Rename AppWindow to MainWindow
BufferViewPlugin => ViewPlugin
Add ViewPlugin::current() and setCurrentView()
TextDocumentPlugin -> DocumentPlugin
Add BufferView::textDocument()
Add DocumentPlugin::currentDocument()
Add BufferPlugin::currentBuffer() & setCurrentBuffer()
Rename TreeWidgetPlugin to TreePlugin
Add ConnectionPlugin::connections() & add/removeConnection()
Move FinderPlugin to app/finder
CommanderPlugin: kill TreePlugin dep
SoundPlugin: kill TreePlugin dep
Move TriconPlugin to TreeItem
TreePlugin is no more
Add communiAddStaticPlugin()
Cleanup & reorganize .prf files
Move TreeXxx back to the app side