Additional options for "Move groups.."

[westram]

Source groups:

• move only groups listed in "group search" (have to be members from one )
• move selected group (via AWAR_GROUP)

Targets options:

• do not overwrite groups (i.e. skip transfer in target node occupied by existing group)
• only overwrite groups (i.e. only transfer group if target node occupied by groups)
  (or somehow score-up overwrites)
  Could be useful to replace "generated groups" by groups from a real .

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related: #792