Consider Having LayerMasker.Layers Take a StartingLayer Field

[Chris3606]

Currently, the LayerMasker only takes a number of layers, not a starting layer. This means that, if you pass uint.MaxValue to LayerMasker.Layers(), it will return layers below a minimum layer, if you are using one.

LayeredSpatialMap gets around this by using a couple layer maskers and also doing bit-shifts on values incoming. However, a simple mask >> startingLayer << startingLayer would remove them entirely from the mask.

In order to gain more intuitive behavior, it may be useful to have LayerMasker implement support for a starting (minimum) layer specifically.