App: add Expression built-in function mscale/minvert/create

mscale(matrix,vector|tuple) for scaling matrix

minvert(matrix|placement|rotation) for inverting matrix, placement or
rotation

create(type,arg...) for creating Python object of given type (currently
only support 'matrix', 'placement', 'rotation', 'vector'

src/App/ExpressionParser.h

@@ -269,6 +269,9 @@ public:
         CATH,
         LIST,
         TUPLE,
+        MSCALE, // matrix scale by vector
+        MINVERT, // invert matrix/placement/rotation
+        CREATE, // create new object of a given type
 
         // Aggregates
         AGGREGATES,