Added support to work as a heat map.

There are 3 new input variables on the Map block:

• HeatMapPointsList (mandatory) - the list of the coordinate points to the heat zones
• HeatMapRadius (optional) - the radius of the circle around the identified zones
• HeatMapOpacity (optional) - the opacity of the circle

• Fixed the preview image for the map on the Service Studio, which was not showing up on the maps' blocks inside its consumers
• Fixed a conflict when using this component together with Google Places Mobile component
• Added the "ShowDefaultMarkers" input parameter to the Map block, which allows to use different markers and pin-points in the middle of the path

Implemented logic to address Google Maps requirement to have a valid API key for all projects.

• Set a default API Key using the GoogleMaps' Site Property, or set an API Key per application.

• Added error handling to the API load (Minor behavior breaking change)
• New MapOnError event 
• Removed unused variable
• Fixed bug regarding SingleLocationMap OnDestroy event (was not clearing Timeout reference)