connect multi-vtd islands

[happyjack27]

detect islands that aren't connected to the biggest region, and connect them (make the closest vtd's neighbors)

i'd say start with the biggest block, and connect up the closest un-connected and spread out from there. (always the closest unconencted to the biggest block)

maybe this feature could be turned on or off.

[happyjack27]

code is in feature.FeatureCollection.initwards().

doesn't seem to be working right. (tried on wisconsin, expected 2 islands, got 38)

uses breadth-first search 'cause i was too lazy to make a recursive function.