allow to revert properties to last saved state

[westram]

• add menu entry to 'Properties' menu (next to 'save properties')
  ⇒ revert all properties to saved state
• add 'Last saved'-button to config-managers (next to 'Factory defaults')
  ⇒ revert managed properties to saved state

Implementation:

• open properties (again)
• copy existing AWAR entries
• reset missing AWAR entries to (hardcoded) default

Optional features:

• reset all properties to factory default (global)
• auto-save managed properties before calling restore, factory defaults or last saved
  • save into temp. entry which will not be saved
  • use special name, e.g. %b4_restore_<timestamp>

Notes:

• "reset to default" does not make sense for database-awars! (would e.g. reset database-comment and similar).
  It's ok when using 'Last saved'-button in config-manager. If config really contains any database awar, resetting it most likely makes sense as well.
• mapped awars shall be handled special:
  • restore default/savedValue of target awar
  • one example for unwanted behavior can be found in the SAI calculator:
    goto its config manager and restore factory defaults
    ⇒ error because mapped awar is overwritten with "" (= default of mapped awar)