Remove DMM from contrib/

This code was never integrated in Dynare. Also, the authors would like to
release a new version soon, and they prefer that we remove this old version
from our repositories.

Closes: #568

.gitmodules

@@ -7,9 +7,6 @@
 [submodule "contrib/ms-sbvar/TZcode"]
 	path = contrib/ms-sbvar/TZcode
 	url = ../../contrib/TZcode.git
-[submodule "contrib/dmm"]
-	path = contrib/dmm
-	url = ../../contrib/dmm.git
 [submodule "matlab/utilities/tests"]
 	path = matlab/utilities/tests
 	url = ../../Dynare/m-unit-tests.git

dmm @ ea7846fd

-Subproject commit ea7846fd71d32851877cf60008ac5046b51a7a51

license.txt

@@ -455,33 +455,6 @@ Files: contrib/ms-sbvar/TZcode/MatlabFiles/qplot2.m
 Copyright: 1997-2012 Clark A. Burdick
 License: GPL-3+
 
-Files: contrib/dmm/*
-Copyright: 2010-2014 European Commission
-           2006-2012 Dynare Team
-License: GPL-3+
-
-Files: contrib/dmm/randlib/*
-Copyright: none
-License: public-domain-dmm
- We place the Randlib code that we have written in the public domain.  
- .
-                                 NO WARRANTY
- .    
-     WE PROVIDE ABSOLUTELY  NO WARRANTY  OF ANY  KIND  EITHER  EXPRESSED OR
-     IMPLIED,  INCLUDING BUT   NOT LIMITED TO,  THE  IMPLIED  WARRANTIES OF
-     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK
-     AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS  WITH YOU.  SHOULD
-     THIS PROGRAM PROVE  DEFECTIVE, YOU ASSUME  THE COST  OF  ALL NECESSARY
-     SERVICING, REPAIR OR CORRECTION.
- .    
-     IN NO  EVENT  SHALL THE UNIVERSITY  OF TEXAS OR  ANY  OF ITS COMPONENT
-     INSTITUTIONS INCLUDING M. D.   ANDERSON HOSPITAL BE LIABLE  TO YOU FOR
-     DAMAGES, INCLUDING ANY  LOST PROFITS, LOST MONIES,   OR OTHER SPECIAL,
-     INCIDENTAL   OR  CONSEQUENTIAL DAMAGES   ARISING   OUT  OF  THE USE OR
-     INABILITY TO USE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA OR
-     ITS ANALYSIS BEING  RENDERED INACCURATE OR  LOSSES SUSTAINED  BY THIRD
-     PARTIES) THE PROGRAM.
-
 License: BSD-2-clause
  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are