[FEATURE REQUEST] Copy/move conflict solved by users

[jesmrec]

Related with #3946

Current behaviour:

Copy/Move a item to a target folder that contains another item with the same name -> (2) is automatically added to the file name to fix the collision

New behaviour (implemented in the oCIS web):

Showing this kind of dialog:

Skip -> cancel operation
Replace -> that's it, put the new one over the existing one
Keep both -> current behaviour

This behaviour does not depend on the kind of backend (oCIS/oC10)

Conflict solving dialog could be reused for this

TASKS

• Research (if needed)
• Create branch feature/file_conflict_solving
• Development tasks
  • Look for the code that checks whether the file exists or not
  • Instead of directly renaming it, return this information to the fragment
  • Create a new dialog to let the user choose the way to solve the conflict
  • Implement "Skip" option
  • Implement "Replace" option
  • Implement "Keep both" option
• Code review and apply changes requested
• Design test plan
• QA
• Merge branch feature/file_conflict_solving into master