deduplication does not work when comparing tags across tiles/layers

[mapsam]

Right now we're comparing tag integers between features to determine if they share the same properties. Unfortunately tag integers are not shared on a global space (tileset) and are only shared within a tile. For example 0, 0 might map to type, road in one tile, but it maps to color, purple in another tile.

For now, let's start by decoding properties and comparing them directly. This will likely result in a pretty significant slowdown, but will actually perform deduplication in the way we want.

cc @flippmoke