As discussed offline, I merged this into the private repo.

Looks like its working as expected. Should this be reviewed?

https://bitbucket.org/flogo/downward-issues/pull-requests/13/issue623/diff

I would like to add an option "DISABLE_PLUGINS_BY_DEFAULT" that disables plugins
by default. This will make it easier to define configurations where only one
feature is active.

Example:
  -DDISABLE_PLUGINS_BY_DEFAULT=YES
  -DPLUGIN_BLIND_SEARCH_HEURISTIC_ENABLED=YES
instead of
  -DPLUGIN_BLIND_SEARCH_HEURISTIC_ENABLED=YES
  -DPLUGIN_LMCUT_HEURISTIC_ENABLED=NO
  -DPLUGIN_ADDITIVE_HEURISTIC_ENABLED=NO
  ...

I'm not quite sure if this will work because of the order in which options are
parsed and created in CMake, but I'll try.