Branch/performance

@BrettASwift @kadst43 would you mind reviewing?
Well, in this case, the difference is between a normal read of a variable and a `get` of a VWF property (which goes to the kernel and cycles through the model drivers to find the value ... which you had expressed concern about before).  It turns out that in some cases, avoiding the repeated `get` is worthwhile ... since this code (the `animationTime` getter) is called so frequently, anything that we can do to speed it up is worthwhile.