Improvement: easy check for continuity

[Bibi56]

curl -s "http://ra.osmsurround.org/analyzeRelation?relationId=1083417&_noCache=on" | grep "Graph " | wc -l tells me if the Oise river is correct (result=1) or (as now) split into chunks (result>1). Great to be able to do that ;-).

Having a JSON output would make life easier. http://ra.osmsurround.org/analyzeRelation?relationId=1083417&_noCache=on&output=json (or filtering : http://ra.osmsurround.org/analyzeRelation?relationId=1083417&_noCache=on&output=text&filter=graph_count) => 2