OpenGLRenderer : Add support for highlighting selected objects
OpenGLRenderer : Add support for highlighting selected objects

It _might_ be worth caching the result of the selection match on the OpenGLObject class, but profiling with VTune suggests that the work done by `PathMatcher::match()` is fairly insignificant compared to the cost of the subsequent GL calls (~1%).

andrewkaufman/gaffer,boberfly/gaffer,appleseedhq/gaffer,hradec/gaffer,GafferHQ/gaffer,hradec/gaffer,andrewkaufman/gaffer,boberfly/gaffer,appleseedhq/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,hradec/gaffer,appleseedhq/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,boberfly/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,ImageEngine/gaffer,lucienfostier/gaffer,ImageEngine/gaffer,hradec/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,lucienfostier/gaffer,hradec/gaffer,appleseedhq/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,boberfly/gaffer