Drop indentations in message definitions

[ZHOUYue67]

Indentations in message definitions do not play well with some of ROS tools & libraries (such as rosbag's python implementation & ros_type_introspection). ros_msg_utils in rosnodejs already generates definitions without indentations, but a lot of users will still use gennodejs.

gennodejs/src/gennodejs/generate.py

Lines 701 to 713 in 779c415

	def write_message_definition(s, msg_context, spec):
	with Indent(s):
	s.write('static messageDefinition() {')
	with Indent(s):
	s.write('// Returns full string definition for message')
	definition = genmsg.compute_full_text(msg_context, spec)
	lines = definition.split('\n')
	s.write('return `')
	for line in lines:
	s.write('{}'.format(line))
	s.write('`;')
	s.write('}')
	s.newline()

[ZHOUYue67]

Related issue in rosnodejs:
RethinkRobotics-opensource/rosnodejs#38

[ZHOUYue67]

I can do a pull request. But first I need some comments and feedback from other people.