rules 7.x-2.0-rc2

Changes since 7.x-2.0-rc1:

• #1258284 Can't edit rules due to internal server error since 7.x-2.0-rc1.
• #1276522 patch by mr.baileys: fixed typo on add event form.
• #1098104 Data comparison of updated and unchanged entity fails if data to compare or data value is empty.
• fixed unknown actions to properly fail the integrity check. For that to work, dropped the undocumented possibility of executing not registered actions or conditions.
• #1270042 follow-up: update dirty flag on rule-display too.
• #1270042 Rules remain dirty and are not executed even if they have been fixed.
• fixed variable name-clash-check to take custom variable names into account when providing variables.
• #1257580 fixed fatal errors FacesExtendable not found if used with the TestingMailSystem.