DOC added vnfrqts/usecases

Adding VNF Requirements Use Cases project
This should be the same level as the VNF Requirements and VNF Guidelines projects
Followed this guide http://onap.readthedocs.io/en/latest/guides/onap-developer/how-to-use-docs/include-documentation.html#setup-project-repositories-s

Issue-ID: VNFRQTS-154

Change-Id: If9205dd4c533944085af639af413141a8ee0db88
Signed-off-by: Bozawglanian, Hagop (hb755d) <hb755d@att.com>
diff --git a/.gitmodules b/.gitmodules
index 3fde0c9..0fe7517 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -314,3 +314,6 @@
 [submodule "docs/submodules/vnfrqts/testcases.git"]
 	path = docs/submodules/vnfrqts/testcases.git
 	url = ../vnfrqts/testcases
+[submodule "docs/submodules/vnfrqts/usecases.git"]
+	path = docs/submodules/vnfrqts/usecases.git
+	url = ../vnfrqts/usecases