Fix group operators

[0joshuaolson1]

https://picolabs.atlassian.net/wiki/display/docs/Group+Operators compiles and doesn't break the engine AFAICT, but the one test I did with repeat n doesn't use the current n when the ruleset using this feature is modified to have a larger n.

[farskipper]

Once the rule matches it won't reset if you change n. However, if you set n=2 signaled one event, then changed it to 10 you'll need to signal 9 more events before it will evaluate the rule body.

This is b/c all select when state machines only remember their current state. Rather than using an event log to recover it's current state. If we provide a built in event log (see #17) we could fix this.