* Fix bug in hierarchical searches using sheet path pointers which are
  destroyed on every search.  Use human readable path as last sheet found
  in test to prevent comparison of deleted pointers.
* Fix a bug in SCH_COMPONENT::Matches() that would prevent searching for
  pins if the search all fields flags was not set.
* Fix a bug in SCH_COMPONENT::Matches() to use the sheet path to perform
  the comparison to the correct reference designator and unit number.
* Fix wrapping in sheet path and sheet path list MatchNextItem methods.
* Push search methods down to EDA_ITEM object so advanced searching can
  be performed on all items derived from EDA_ITEM.
* Add virtual method to EDA_ITEM object to test if item supports replacing
  text.
* Replace switch statement magic numbers in Eeschema socket connection code
  with Pcbnew for improved readability.