Split "widgets" to "widget" and "controller"

Split inner widgets (like MaEditorSequenceArea, MaEditorNameList and so on) to a controller and a widget. Widget is required for drawing, Controller is required for working with several widgets. The good place where it's done well is MSAEditorOffsetsViewWidget and MSAEditorOffsetsViewController. 

The attached "plan.diff" file contains information what class - "widget" or "controller" - members of current classes should be moved to.