Pass BUILDNAME and SITE options along to CTest/CDash

By passing these options through ./configure, one can use dunecontrol
to build a complete stack and still get a customized description in
CDash (such as when building in a cluster or VM where the actual machine
name does not matter, or when you want to add key options to the name
shown) without having to run a second configuration just to set those
in the cache.

Also fixes a bug where --with-cmake would skip any further option
specified after it.
Merge pull request #26 from bska/026_cmake

Synchronise build system with opm-core