group markers description

This version introduces multiple enhancements:

each dynamic marker has own description cloud
changed descriptions
refactored render group markers

Details of additions/deletions below:
--------------------------------------------------------------

Modified:   js/markers.js
            -- Updated --
                changed descriptions

Modified:   js/maps.js
            -- Added --
                createGroupMarker to render group markers with their descriptions
            -- Updated --
                drawMarkers used function createGroupMarker