Cleanup unused code

[hansmorb]

Let's collect some unused classes / functions here in order to deprecate them in 2.11 and remove them in 2.12.

• MapFilter class
• CB1UserFields
  • set_basic_user_vars
  • add_user_vars
• Helper/WordPress::getLocalDateTime
• Migration class (see Migration rauschmeissen #1748)
• CB/CB1UserFields.php (see CB1 User Feld entfernen #1749)
• Model/CustomPost
  • setDate, getDate and the $this->date field (unused)
• Model/Item::getRestrictions ; Model/Location::getRestrictions (Restrictions are never retrieved purely by item / location)
• Model/Restriction
  • isLocked
  • getItemName ( accessed through {{item:post_title}} template tag over Item Model, not this method)
  • getLocationName ( can be accessed through {{location:post_title}} template tag, not needed here)
  • Repository/CB1 class (see Migration rauschmeissen #1748)