Revert "YAMLParser: run cleanup after generating Messages.dll to allow message definition subtraction from the msg "cache""

This reverts commit 5f9eee7fd8b39904ae0c63ff45a0bbee514b9e1a.
Use a pathmap for message dependancies (stick a ROS_MESSAGES_ROOT.txt file in the solution dir with a list of paths to recurse into inside of it)
testmsgs are vestigial
msg_gen: fix behavior when solution directory (passed as argument by visual studio) does not contain a ROS_MESSAGE_ROOT.txt file
msg_gen+YAMLParser: rebase fixup