* Change all code references to pin sheet and sheet label to sheet pin to
more closely match the sheet pin object for improved code readability.
* Change menu and tool bar text from pin sheet to sheet pin for improved
user readability.
* Moved sheet pin place method to sheet pin object source file.
* Move last sheet pin stored state information into schematic frame object.
* Add Doxygen comments for the sheet pin editing methods.
* Add item clarification context menu to EESchema when multiple unresolved
items are found at the current cross hair position.
* Add collector class SCH_COLLECTOR for supporting multiple item hit testing.
* Removed bit wise masked filtering from schematic item hit testing.
* Removed all old hit testing functions and methods scattered about the
EESchema source code.
* Move terminal point test function into SCH_SCREEN object.
* Fixed bug in terminal point test when terminating a bus to a label.
* Define the < operator for sorting schematic items.
* Add area calculation method to EDA_Rect item.
* Add method for returning an item's bitmap for menu display purposes.
* Add method for returning an item's menu text for menu display purposes.
* Changed EDA_ITEMS container from boost::ptr_vector to std::vector.
* Factor coordinate string conversion code from EDA_DRAW_FRAME to function
CoordinateToString().
Wayne Stambaugh