GEOMESA-151 allowing schema to not be set in datastore config for already created features

Since geoserver doesn't even have the ability right now to configure a custom schema.
getOrElseUpdate - nice function to know about :)

for iterating over the 'checks', would it be something like:

val checks = List(checkVisibilitiesMetadata(featureName), checkSchemaMetadata(featureName))

where the two check functions return Option[String] ?