decouple metapanel to a independent "feature" container for segments

Currently interactions between metapanel, editing a segment and commenting a segment are distributed across all affected controllers. All above mentioned parts are tightly coupled to each other.
This should be redesigned, so that:

• The MetaPanel Controller is divided into a
  • MetaPanel Container, which is the surrounding container, and corresponding controller handles open and close requests to the whole MetaPanel or single subpanels (for example comments on read only segments)
  • Segment MetaPanel: The Panel with Terms, QMs etc. which is currently known as MetaPanel
• Comment Component may not contain code to open close etc. the panel

This gives us a more clean code structure, enables an easier switch to ExtJS 5 (in this part of the application) and enables us to add easily more subpanels for plugins.