Removed terminal-colors.h

There were 2 problems:

- it does not belong into a numerical library
- the approach with hardcoded escape codes is not portable even on Linux

There are separate libraries which solve both of these issues much more
nicely, they should be used instead.

src/TNL/terminal-colors.h

-/***************************************************************************
-                          terminal-colors.h  -  description
-                             -------------------
-    begin                : Feb 7, 2015
-    copyright            : (C) 2015 by Tomas Oberhuber
-    email                : tomas.oberhuber@fjfi.cvut.cz
- ***************************************************************************/
-
-/* See Copyright Notice in tnl/Copyright */
-
-#pragma once
-
-namespace TNL {
-
-const String red( "\033[0;31m" );
-const String green( "\033[1;32m" );
-const String yellow( "\033[1;33m" );
-const String cyan( "\033[0;36m" );
-const String magenta( "\033[0;35m" );
-const String bold();
-const String reset( "\033[0m" );
-
-} // namespace TNL
-