Add premake support to build pybullet, Windows and Linux tested, will enable Mac in next commit.

Expose inverse dynamics to Bullet shared memory API, through b3CalculateInverseDynamicsCommandInit and
b3GetStatusInverseDynamicsJointForces command/status. See PhysicsClientExeample or pybullet for usage.
Add option for Windows and Linux to set python_lib_dir and python_include_dir for premake and --enable_pybullet option
Expose inverse dynamics to pybullet: [force] = p.calculateInverseDynamics(objectIndex,[q],[qdot],[acc])
Thanks to Jeff Bingham for the suggestion.

examples/SharedMemory/SharedMemoryPublic.h

@@ -27,6 +27,7 @@ enum EnumSharedMemoryClientCommand
     CMD_REMOVE_PICKING_CONSTRAINT_BODY,
     CMD_REQUEST_CAMERA_IMAGE_DATA,
     CMD_APPLY_EXTERNAL_FORCE,
+	CMD_CALCULATE_INVERSE_DYNAMICS,
     CMD_MAX_CLIENT_COMMANDS
 };
 
@@ -59,6 +60,8 @@ enum EnumSharedMemoryServerStatus
         CMD_BODY_INFO_COMPLETED,
         CMD_BODY_INFO_FAILED,
 		CMD_INVALID_STATUS,
+		CMD_CALCULATED_INVERSE_DYNAMICS_COMPLETED,
+		CMD_CALCULATED_INVERSE_DYNAMICS_FAILED,
         CMD_MAX_SERVER_COMMANDS
 };