Tests needed for config_install:

   __init__():
      - sets up env: __target_host

   cleanup()
      - Fail if cache_dir from previous run cannot be deleted
      - Fail if cache_dir cannot be created from current out_dir

   filter()
      - ensure logformat is changed: target host is prefixed:
         LOGLEVEL: target_host: MESSAGE

   run_initial_manifest():
      - parameter is actually used (from __init__)
      - ensure changing the manifest actually runs a different manifest
      -> give ConfigInstall Constructor different manifest
         -> different manifest is executed.
      - test all submitted (from core to type manifest) variables:
         - ENVIRONMENT
         - they are set
         - they contain the correct values

   run_type_manifest():
      - test all submitted (from core to type manifest) variables:
         - ENVIRONMENT
         - they are set
         - they contain the correct values
   run_manifest():
      - test all submitted variables:
         - ENVIRONMENT
            - including __debug, if debug
         - they are set
         - they contain the correct values
      - does $require work?

   transfer_type_explorers():
      - Explorers are not transferred twice
      - No transfer tried if there are no type_explorers

   emulator()
      may only be called with __ as prefix - fail otherwise!

   object_run():
      - ensure no object is run twice
      - ensure requirements are taken into account?
         - and order of run is adjusted
      - check (from extern?) that all needed variables are setup
      - ensure no code-{local, remote} is created, 
         if gencode is not producing code
      - ensure THAT code-{local, remote} contains what gencode created
      - abort if gencode-* fails
      - abort if code-* fails
         - abort == raise(FooException)
      - gencode-*: ensure ENVIRONMENT is setup correctly

      run_type_explorer(): ensure output is saved to correct path
      run_type_explorer(): ensure a type with no explorers works
      run_type_explorer(): ensure environment is setup correctly


      all: check that messages of all functions contain target_host in string

   config_install:
      run_type_manifest() - same tests as for test_initial_manifest_*?
      run_manifest() - raise exception if manifest is not existent