Reimplemented Gaffer.Path and Gaffer.PathFilter in C++.
Added RunTimeTyped registrations for all python Path types.
Added binding for Path::emitPathChanged().

ScenePathTest passes!
Fixed PathFilter::changedSignal() binding.
Implemented FileSystemPath.copy().

All path classes will have to define a proper copy method now the base class is in C++.
Fixed GafferTest.PathFilterTest.

It was using an empty directory, and therefore testing nothing much at all.
Implemented PathFilter::filter() binding.
Beefed up GafferTest.CompoundPathFilterTest.

It wasn't actually testing filtering at all.
Dealing with dict->CompoundData user data in PathFilterWidget.
Fixed Path::items() to be const.
Added missing include to PathFilter.h
Added GafferBindings::PathClass to simplify Path bindings.
Reimplemented GafferScene.ScenePath in C++. WIP.
Extended Path lazy signalling to allow derived classes to use it too.
Got ScenePath signalling working.
FileSystemPath in C++. WIP - needs filters in C++ and attribute queries.
CompoundPathFilter WIP
FileSystemPathBinding fix.
CompoundPathFilter done.
Added pointer declaration for CompoundPathFilter.