Change git submodule to relative path

.gitmodules

 [submodule "openfpm_vcluster"]
 	path = openfpm_vcluster
-	url = ssh://git@git.mpi-cbg.de/openfpm/openfpm_vcluster.git
+	url = ../openfpm_vcluster.git
 [submodule "openfpm_devices"]
 	path = openfpm_devices
-	url = ssh://git@git.mpi-cbg.de/openfpm/openfpm_devices.git
+	url = ../openfpm_devices.git
 [submodule "openfpm_io"]
 	path = openfpm_io
-	url = ssh://git@git.mpi-cbg.de/openfpm/openfpm_io.git
+	url = ../openfpm_io.git
 [submodule "openfpm_data"]
 	path = openfpm_data
-	url = ssh://git@git.mpi-cbg.de/openfpm/openfpm_data.git
+	url = ../openfpm_data.git
 [submodule "openfpm_numerics"]
 	path = openfpm_numerics
-	url = ssh://git@git.mpi-cbg.de/openfpm/openfpm_numerics.git
+	url = ../openfpm_numerics.git
 [submodule "gdbgui"]
 	path = gdbgui
 	url = https://github.com/incardon/gdbgui.git