Always use JSON gem for pretty_generate in web_console

Not every MultiJSON implementation supports pretty printing.
Fix showing flow step error
Fix desc ordering

The Sequel constant was resolved to the wrong object. Using ::Sequel instead.
Show and order by started_at time.
Fix re-running finalize phase

We need to reset the states on the finalize phase before running it
because we run the finalize only when there were no steps in error state.

Also because the finalize runs in transaction, we rerun also finished
finalize steps.
Support multi-subsribe

One action can subscribe to more actions.
Use pretty_inpsect instead of JSON.pretty