Improve VBO field settings (fix issues with dependent settings and  advanced actions, custom settings provided by actions; remove unused function)

Cleaner handling of default values in VBO admin. Fixes a bug with 'Override label' being selected by default when a new operation is selected.

Update default views to remove my test rules actions that got there by mistake, and to make the Published filter on the Content view default to 'All' instead of 'No'.

Removed the VBO_AGGREGATE_FORCED / VBO_AGGREGATE_FORBIDDEN / VBO_AGGREGATE_OPTIONAL constants. The 'aggregate' flag is now a boolean.

Improve the usability of the override label functionality (by making it match the Views UI guidelines).

Port the VBO configuration form changes from 6.x-1.x, allowing custom labels and confirmation skipping per action.

Enable the delete action by default on the default VBO views. Fix a bug causing the message after an action to always say that 1 row was modified.

Issue #724686 by dafeder, bojanz - Add a 'force single' option, making VBO show radios instead of checkboxes

Core actions integration: Add back support for the 'behavior' key, save explicitly all entities that need to be saved (as specified through behavior).

Use operation type 'entity' instead of 'system' for actions that work on all entity types. That matches the Rules terminology.

Update the default views (the default content view was throwing a notice), point the user to them in the README.