[bugfix,documentation] Ship the image files with the gg_ prefix

These are the ones actually used in the doxygen documentation.
gg_ stands for 'genericgeometry_'.  The ones without the prefix show
the old numbering used before the advent of the generic implementation.
(cherry picked from commit 7566dc8c3ce33a289c17ab0c9b760565199c3ff6)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[buildsystem,release] Generate cmake package configuration files with autotools
(cherry picked from commit 0a0eb89d69b9b8507fc6a5b08c9bb8223dd83f9c)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[autotools,bugfix] correct path to cmake directory

There was just missing the $(top_srcdir) var.
(cherry picked from commit f4a7f1d0f1ff8b3ed24af4e6366ca59216f158ae)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>