Update plugin for biocache-service offline ws additions

[adam-collins]

Change the way this plugin handles offline downloads that exceed the biocache-service limit.

When /occurrences/offline/download receives a request that is too large it responds with

{ 
	"status": "skipped",
	"message": "{defined in biocache-config.properties}"
	"error": "Requested to many records ({query record count}). The maximum is ({max defined in biocache-config.properties}).",
	"searchUrl": "{url to search request}",
	"downloadUrl": "{url to downloads.ala.org.au or other as configured in biocache-config.properties}"
}

The maximum is available from a GET to /config, e.g.

{
	"download.offline.max.size": 100000000
}