Deprecate the file configparser.hh

Use parametertree.hh to keep hierarchical string-based data, 
and parametertreeparser.hh to read such data from files and streams.

[[Imported from SVN: r6347]]

dune/common/configparser.hh

@@ -3,6 +3,11 @@
 #ifndef DUNE_CONFIGPARSER_HH
 #define DUNE_CONFIGPARSER_HH
 
+#warning This file has been deprecated in dune-common 2.1, and will most likely\
+  be removed in dune-common 2.2.  In its place, use parametertree.hh to keep\
+  hierarchical string-based data, and parametertreeparser.hh to read such data\
+  from files and streams.
+
 #include <iostream>
 #include <istream>
 #include <map>