Add MUSIC project submodule and toctree refs

Change-Id: I88174a9eae28b4cf212ad6059d36b3ffff101ff1
Signed-off-by: Rich Bennett <rb2745@att.com>
Issue-ID: DOC-253
diff --git a/.gitmodules b/.gitmodules
index d62bc88..7042def 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -298,3 +298,8 @@
 	url = ../vfc/nfvo/driver/vnfm/svnfm
 	branch = .
 	ignore = dirty
+[submodule "docs/submodules/music.git"]
+	path = docs/submodules/music.git
+	url = ../music
+	branch = .
+	ignore = dirty