* Create single event handler for grid size events.
* Fix all frame windows to use new grid size event handler.
* Use offset relative to ID instead of ComboBox index to save last grid size.
* Move last grid size load/save setting into WinEDA_DrawFrame.
* Add equality and assignment operators the GRID_TYPE.
* Add current grid helper methods to BASE_SCREEN.
* Add GetPins helper to LIB_COMPONENT to replace GetNextPin where applicable.
* Add AppendMsgPanel helper to WinEDA_DrawFrame.
* Improve rounding for display of coordinates when millimeter units are selected.