[TASK] Allow empty action configuration

Since we use the default action handling of Extbase no action
configuration is required.

To make sure everything still works the action settings array is
initialized with an empty array if no settings were found.
[TASK] Cleaned up TypoScript configuration

The defaultPid configuration was moved to the correct place
(view.defaultPid) and some obsolete settings (useAction) were removed.
[BUGFIX] Return event status as string

Since returning the event status as an instance of the EventStatus
enumeration can cause trouble in Fluid (e.g. in comparisons) we convert
the status to a string before returning it.