Validation rules: Add OR logic

[davidzbiral]

We sometimes need to require users to:

• reference Resource A or Resource B - any will do, but at least one ref. to either Resource A or B is required;
• either property occupation or property office - any of the two is OK.
  This requires to include, into each rule, the possibility of multiple values in OR logic.
  A complication is properties, which have an OR already on propvalues, so what it means to put an OR on the proptype too - I guess that the correct solution is that any combination of proptype and propvalue stated here passes the test.

Add this OR also to the textual description of the rule that the app builds for the users (such as "Any Action must have a reference to Resource WordNet 3.0 Synset IDs.").