* Remove specialized edit reference, value, and foot print field methods
  from SCH_FRAME object.
* Improve general field method to handle all field types as this was
  essentially the same code used in the three methods removed.
* Updated the the hot key and context menu handlers to use the new field
  edit method.
* Minor Doxygen comment warning fixes.

fix 2 minor bugs: GERBVIEW: Button "Erase all layers" not working, EESCHEMA: Plot to Clipboard: EDA_DRAW_FRAME::PrintPage() error

* Push schematic back annotation code down into the appropriate class.
* Minor improvements to back annotate file selection code and user prompt
  strings.
* Minor tool bar tool tip capitalization fixes.
* Change tool bar ID error from message dialog to a debug assert message.

* 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().

F1.) Allows you to disable a component from the Netlist.  Useful for connectors etc.
To exclude a component from the Spice Netlist add [Spice_Netlist_Enabled] user FIELD set to: N

F2.) Allows you to adapt to simulation libraries that require the netlist node 
sequence to be in a different order. To reorder the component spice node sequence 
add [Spice_Node_Sequence] user FIELD and define sequence: 2,1,0  I am using 
LTSpice, but this holds true for any SPICE subcircuit.

Eeschema: fix a *very serious* bug in netlist generation: sometimes the netlist forgets pins for components having more than one part per package, in hierarchical designs.

Gerbview:   Added: read Excellon files created by Pcbnew. The full Excellon command set is not supported, but drill files created by Pcbnew are supported.