Passing around a pointer was leading to crashes as the ASVC was the sole owner of the context. There are cases where the VC would dealloc while its subnodes were laying out. This could lead to the subnodes accessing a garbage pointer.
* make variable naming reflect ASEnvironmentTraitCollection vs ASTraitCollection
* move trait propagation to cell allocation instead of via a nested block
* move trait propagation when setting a displaynode's supernode instead of when adding a subnode
* fixed misspelling of "colection"
