Create new contrib folder & move ms-sbvar submodules there

.gitmodules

-[submodule "ms-sbvar/utilities_dw"]
-	path = ms-sbvar/utilities_dw
+[submodule "contrib/ms-sbvar/utilities_dw"]
+	path = contrib/ms-sbvar/utilities_dw
 	url = http://www.dynare.org/git/frbatlanta/utilities_dw.git
-[submodule "ms-sbvar/switch_dw"]
-	path = ms-sbvar/switch_dw
+[submodule "contrib/ms-sbvar/switch_dw"]
+	path = contrib/ms-sbvar/switch_dw
 	url = http://www.dynare.org/git/frbatlanta/switch_dw.git

license.txt

@@ -138,15 +138,15 @@ Copyright: 2009 John Burkardt
            2010-2011 Dynare Team
 License: LGPL-3+
 
-Files: ms-sbvar/utilities_dw/*
+Files: contrib/ms-sbvar/utilities_dw/*
 Copyright: 1996-2011 Daniel Waggoner
 License: GPL-3+
 
-Files: ms-sbvar/switch_dw/*
+Files: contrib/ms-sbvar/switch_dw/*
 Copyright: 1996-2011 Daniel Waggoner and Tao Zha
 License: GPL-3+
 
-Files: ms-sbvar/switch_dw/state_space/sbvar/dw_csminwel.c
+Files: contrib/ms-sbvar/switch_dw/state_space/sbvar/dw_csminwel.c
  state_space/sbvar/dw_csminwel.h
 Copyright: 1996 Christopher Sims
            2003 Karibzhanov, Waggoner and Zha

mex/build/ms_sbvar.am

 noinst_PROGRAMS = ms_sbvar_create_init_file ms_sbvar_command_line
 
-DWSWITCHDIR = $(top_srcdir)/../../../ms-sbvar/switch_dw
-DWUTILITIESDIR = $(top_srcdir)/../../../ms-sbvar/utilities_dw
+DWSWITCHDIR = $(top_srcdir)/../../../contrib/ms-sbvar/switch_dw
+DWUTILITIESDIR = $(top_srcdir)/../../../contrib/ms-sbvar/utilities_dw
 
 DYNMEXSRCDIR = $(top_srcdir)/../../sources
 MSMEXSRCDIR = $(DYNMEXSRCDIR)/ms-sbvar