Search for module in suite directory if specified

Instead of having to specify each and every project in a suite such as
DUNE or OPM, allow a root directory for the entire suite to be specified
and then assume that each module is located in a sub-directory to this.

Each individual project can still have its path explicitly specified, if
a special build of those are required.

The suite variable itself will be written to cache by being specified
on the command line. Each individual project directory will NOT be
written to cache, because then we cannot get rid of it by specifying a
new suite directory.
Provide suite info for those not in name convention
Teach configure wrapper to know about modules
Give better diagnostics in case probe fails

The standard argument handling report which item that failed
(_INCLUDE_DIR, _LIBRARY og HAVE_) but it doesn't provide information
about the root that was used to search for these. Given that we now
automatically search a lot of other places, the _ROOT variables should
be reported before the error is raised.
Allow packages to be installed directly in suite dir

Let us specify e.g. --with-dune=/usr, so that the _ROOT variable is
set to e.g. /usr/dune-common, but then backtrack to the parent directory
again if we don't find anything there and search directly in suite dir.
Also look in corresponding build-dir as ourself

If we are building in a sub-dir to the source tree, guess that a
dependent module is also that, and that the directory that is given
is for the suite, not for the project alone.
Merge pull request #45 from rolk/045_suite

Allow to specify directory for all projects in a suite with one parameter