- undo redo now works fine for both measure tool creation commands - added LayerHolder to streamline layer index management - added overloads for ORTHANC_ASSERT with no string message (some heavy preprocessor wizardry in there) - fixing wasm BasicScene is *not* finished.

#define ORTHANC_OVERRIDE
#define ORTHANC_STONE_DEFINE_EMPTY_MESSAGE(FILE, LINE, NAME) class NAME : public ::OrthancStone::IMessage {};