"guards" of Rules should be in their patterns, not outputs

[EasyArray]

Now when a Rule is parsed, the portion after || becomes part of the output of the rule:

phosphorus/phosphorus/__init__.py

Line 37 in 2edba9f

(r'rule +([^ :]+):? +⟦?([^⟧]+)⟧? *(?:=>?|->) *(.+) \|\| +(.+)(?=\n)', r"Rule(\1, \2, '\3 if \4 else None')"),

phosphorus/phosphorus/phival.py

Lines 592 to 593 in 2edba9f

	class Rule(object):
	def __init__(self, name, pattern, output):

I wonder if it should instead be part of the pattern? But that is not possible given that patterns are simply PhiVals as things stand. This ties in to the larger issue of expanding the pattern matching machinery.