Git submodule update: track develop, default rebase policy

.gitmodules

 [submodule "openfpm_vcluster"]
 	path = openfpm_vcluster
 	url = ../openfpm_vcluster.git
+	update = rebase
+	branch = develop
 [submodule "openfpm_devices"]
 	path = openfpm_devices
 	url = ../openfpm_devices.git
+	update = rebase
+	branch = develop
 [submodule "openfpm_io"]
 	path = openfpm_io
 	url = ../openfpm_io.git
+	update = rebase
+	branch = develop
 [submodule "openfpm_data"]
 	path = openfpm_data
 	url = ../openfpm_data.git
+	update = rebase
+	branch = develop
 [submodule "openfpm_numerics"]
 	path = openfpm_numerics
 	url = ../openfpm_numerics.git
+	update = rebase
+	branch = develop
 [submodule "gdbgui"]
 	path = gdbgui
 	url = https://github.com/incardon/gdbgui.git
+	update = rebase
+	branch = master

gdbgui @ b213761e

-Subproject commit c8048e7898e3a20d1ad1749d82d750e743247d8a
+Subproject commit b213761e4cfeec08d1cf3c40041896eeb76282c9

openfpm_io @ 3da60481

-Subproject commit 8e61e26f8c01efc13fad5a232632cfa0b1d05a90
+Subproject commit 3da604810353ec04eb317e22f5af6195acdde2ac

openfpm_numerics @ c12d45a1

-Subproject commit fcd5202df90e8a693d32db2e336370c885f7ec24
+Subproject commit c12d45a1b425fcc981bca83e2a4fbdee2f7eb08c