add genmsg and gencpp python modules, ros not required anymore for message generation

.gitmodules

@@ -7,3 +7,9 @@
 [submodule "uavcan"]
 	path = uavcan
 	url = git://github.com/pavel-kirienko/uavcan.git
+[submodule "Tools/genmsg"]
+	path = Tools/genmsg
+	url = https://github.com/ros/genmsg.git
+[submodule "Tools/gencpp"]
+	path = Tools/gencpp
+	url = https://github.com/ros/gencpp.git

Makefile

@@ -228,12 +228,15 @@ MSG_DIR = $(PX4_BASE)msg/px4_msgs
 MSG_TEMPLATE_DIR = $(PX4_BASE)msg/templates
 TOPICS_DIR = $(PX4_BASE)src/modules/uORB/topics
 TOPICS_TEMPORARY_DIR = $(BUILD_DIR)topics_temporary
+GENMSG_PYTHONPATH = $(PX4_BASE)/Tools/genmsg/src
+GENCPP_PYTHONPATH = $(PX4_BASE)/Tools/gencpp/src
 
 .PHONY: generateuorbtopicheaders
 generateuorbtopicheaders:
 	@$(ECHO) "Generating uORB topic headers"
-	$(Q) ($(PX4_BASE)/Tools/px_generate_uorb_topic_headers.py -d $(MSG_DIR) \
-		-o $(TOPICS_DIR) -e $(MSG_TEMPLATE_DIR) -t $(TOPICS_TEMPORARY_DIR))
+	$(Q) (PYTHONPATH=$(GENMSG_PYTHONPATH):$(GENCPP_PYTHONPATH) $(PYTHON) \
+		$(PX4_BASE)Tools/px_generate_uorb_topic_headers.py \
+		-d $(MSG_DIR) -o $(TOPICS_DIR) -e $(MSG_TEMPLATE_DIR) -t $(TOPICS_TEMPORARY_DIR))
 # clean up temporary files
 	$(Q) (rm -r $(TOPICS_TEMPORARY_DIR))
 

Tools/gencpp

@@ -0,0 +1 @@
+Subproject commit 26a86f04bcec0018af6652b3ddd3f680e6e3fa2a

Tools/genmsg

@@ -0,0 +1 @@
+Subproject commit 72f0383f0e6a489214c51802ae12d6e271b1e454