Move loader in page
Extract onLoad onLoaded function for json layer
Properly indent code
Remove deprecated icon and popup callbacks
Install tips
Import makerCluster plugin
Clusterize with layerJson.layerTarget to ClusterMarker
Leaflet Cluster Marker integrated ( Merge branch 'Clusterizing')

- add ClusterMarkerGroup leaflet plugin.
- use layerJSon targetLayer option pointing to cluster
  layer.