Add support to inline constraints on multi-function accumulate

FROM MARK:
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Edson,

While I don't want to change to acc/for keyword quite yet, until we are sure what drastic changes we want to make to syntax. I think we can evolve accumulate()
1) make the first ", " optionall [,;]. Where the documented new separate is ";"
2) functions are still "," separated
3) allow an optional second ";" after this boolean expression, an eval without the eval wrapper.

3. can be done now with a separate eval(....) after the accumulate. But I think good to encapsulate the intent of the guard within the accumulate itself, it's also another opportunity to remove the "eval" keyword for a common use case. For now we'll just rewrite the accumulate to place an eval() CE after the acc. It's a small win, which I think will make the DRL look nicer, especially for CEP use cases.

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FROM EDSON:
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Mark,

(1) and (2) are ok. Regarding (3), we can embed the expression in the accumulate node itself. No need for a separate node. And if we use ; as the separator, we don't need the eval() keyword.