Use ssh instead of https for git submodules.

.gitmodules

@@ -12,10 +12,10 @@
 	url = http://www.dynare.org/git/dmm.git
 [submodule "matlab/utilities/tests"]
 	path = matlab/utilities/tests
-	url = https://github.com/DynareTeam/m-unit-tests.git
+	url = git@github.com:DynareTeam/m-unit-tests.git
 [submodule "matlab/particles"]
 	path = matlab/particles
-	url = https://github.com/DynareTeam/particles.git
+	url = git@github.com:DynareTeam/particles.git
 [submodule "matlab/modules/dates"]
 	path = matlab/modules/dates
 	url =  git@gitlab.com:McModelTeam/dates.git
@@ -26,4 +26,4 @@
 	branch = master-with-fame-io
 [submodule "matlab/modules/reporting"]
 	path = matlab/modules/reporting
-	url = https://github.com/DynareTeam/reporting.git
\ No newline at end of file
+	url = git@github.com:DynareTeam/reporting.git
\ No newline at end of file