[CMake] Guess build directory of dune-common

Previously we relied on CMake's export(PACKAGE ...) function when
finding dune packages without dune-control. This is error prone
when using several instances of a dune-module (either with differing
versions or built using different options). In this case there is no
control which of the instances is used.

Now we try to guess the correct build directory, if it was not
provided with ${module}_DIR, ${module}_Root or in the
CMAKE_PREFIX_PATH. Note that when using dunecontrol ${module}_DIR will
always be set. We take the path of the current toplevel build
directory and simply substitute any occurence of the name of current
module with name of the module that we try to find. This works for
both  building in a subdirectory of the source tree
(e.g. ${module-source}/build-cmake) or in a sibling directory
Fixes compilation of dgfwriter utils for gcc-4.1.

Somehow gcc-4.1 tried to invoke the copy construtor of stringstream
when calling
void write ( std::ostream &gridout,
                 const std::stringstream& addParams =
		 std::stringstream() )
without the optional argument. This patch works around this obvious
compiler bug by adding another write method with just one argument.
Merge branch 'feature/FS1306-cmake-guess-builddir'

This merge allows us to get rid off the dubious export(PACKAGE ...)
functionality that gives us now control what module instance is found
(apart from the correct version).