* Create library collector class.
* Add clarification menu to library editor when multiple items are found
  at the current position.
* Add get clarification menu text to all objects derived from LIB_ITEM.
* Add get menu bitmap for all objects derived from LIB_ITEM.
* Improve LIB_PIN bounding box calculation.
* Rename LIB_ITEM::DoGenCopy to doClone to match behavior defined in base
  class EDA_ITEM.
* Minor class renaming for improved code consistency.
* Added less than operator to EDA_ITEM.