Add some HHGear nil checks to teleport.
google bug #974
display circle for custom build dist values, display nothing if no limit. map borders are not taken into account at this point
Lua API: SetMaxBuildDistance([ distInPx ]) -- set to 0 for no limit; call with no param to reset to default
global variable for defining construction distance limit. value smaller 1 means no limit (wip)