- List the cmake modules explicitly (file(GLOB will not detect changes

  after configure)
- Make CMake module installation path configurable
- Detect CMAKE_MODULE_PATH automatically
  + First call find_package(dune-common) to query its CMAKE_MODULE_PATH
  + Then setup the module path
  + After each find_package of dune module update the CMAK_MODULE_PATH
  + each module exports ist own <package-name>_MODULE_PATH in the
  + package configuration files
- Adapted dunecontrol and duneproject accordingly.

[[Imported from SVN: r6996]]