Stabilize fast double parser

[Jolanrensen]

This will be done in two steps:

• First we set the default for useFastDoubleParser in all parser options to true
• Later if we know it's stable in all cases, we can remove this parser option altogether

[zaleslaw]

@Jolanrensen do we need something todo in Beta1? or move to Beta2

[Jolanrensen]

I moved it, part 1 is done for beta1, we can do part 2 when we're sure it's stable enough. Doesn't even need to be beta 2 per se