Pcbnew: fix very minor issue.

* Remove most (not all) variables that were initialized but never used that
  cause GCC 4.6 to generate a warning.
* Fix bug in schematic library editor best zoom calculation.

Minor other fixes.

Pcbnew: bug fix: in rare cases, solid copper areas are to large (minimum width not taken in account to calculate filled areas)

Pcbnew: refresh issue with dialog designe rules under wxWidgets 2.9.2 under WINDOWS (replace wxChoiceBox by wxComboBox, should not change anything for users)
Eeschema: some  issues in libedit (when editing a pin )

Eeschema: bug fix: after a "De Morgan" convert command, the component was left selected (.m_Flags not cleared)

* 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.