PROPERTIES object has been recreated every time it was needed, using
two fields in PART_LIB class. Now the buffering & caching settings are
stored directly in a PROPERTIES object.
* Factor out PROPERTIES object from the PCB plugin code and move it into
common so it can be used by both the Pcbnew and Eeschema plugins.
* Add schematic I/O plugin manager for loading and saving schematic and
component library files.
* Add initial attempt at a parser for current schematic file format. This
parser will be infinitely more strict than the current parser which is very
forgiving in what it parses.
* Make minor changes to the base bitmap class to support the new parser.
* Add find root sheet support to sheet object to allow fetching the root
sheet from any sheet in the stack.
Marek Roszko
Jon Evans
Wayne Stambaugh
Seth Hillbrand
Maciej Suminski
Wayne Stambaugh