improve commenting on readonly segments by unifying segment click actions

The behaviour for clicking on segments should be the following (in normal mode):

• double click on a editable segment: open segment for editing
  • normal mode: open segment metapanel accordion
  • visual review simple mode: just edit segment
• double click on a non editable segment
  • normal mode:
    • open comment accordion if allowed
    • show segment non editable message
  • visual review simple mode: just edit segment
    • show segment non editable message
    • no comment opening, since comments are in a separate window
• single click on a editable segment
  • normal mode: no change in the metapanel
  • visual review simple mode: default behaviour, no comment window
• single click on a non editable segment
  • normal mode:open comment accordion if allowed
  • visual review simple mode: no comment opening, since comments are in a separate window

To full fill these requirements needs some clean up and refactoring in the comments code.

Needed code changes:

• remove loadCommentPanel from expand event
• remove resetting the opened accordion tab
• open the desired accordion tab as defined above
• remove comment panel collapse after comment save success in normal mode on a non editable segment
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