Destroy drop targets on panel destroying
Add separation between a minute (singular) and minutes (plural)

Fixes #749, #751

(cherry picked from commit bdad75950d50242dc3c7965844b2764d4d5e8f37)
Destroy drop targets on panel destroying

Fixes bug introduced by ExtJS 3.4.1.1 upgrade

Merge remote-tracking branch 'origin/pr/763' into release-2.2

* origin/pr/763:
  Destroy drop targets on panel destroying