POC: components for ERT

Use this to not announce ecl_well as a dependency across all projects since symbols only end up in a unit test of opm-core.

@bska POC of what we discussed yesterday. this way the find rule can be synced across projects just fine.
former. list(FIND) is smart enough to consider an empty list as never holding what we search for and will return -1.
notice how it eats the variable name and not its contents. this is exactly so it can handle this.