Major overhaul of the parsing of disjunct expressions

... which it turns out have NEVER worked, and badly written tests were masking the problem. Also tagging rules with metadata as first step towards mixing production and flow rules.

docs/cloverage/mw_parser/declarative.clj.html

@@ -26,7 +26,7 @@
                 007              [mw-parser.generate :refer [generate]]
                 </span><br/>
 <span class="not-tracked" title="0 out of 0 forms covered">
-                008&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[mw-parser.simplify&nbsp;:refer&nbsp;[simplify-rule]]
+                008&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[mw-parser.simplify&nbsp;:refer&nbsp;[simplify]]
                 </span><br/>
 <span class="not-tracked" title="0 out of 0 forms covered">
                 009&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[mw-parser.utils&nbsp;:refer&nbsp;[rule?]]
@@ -443,7 +443,7 @@
                 146&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(let&nbsp;[rule&nbsp;(trim&nbsp;rule-text)
                 </span><br/>
 <span class="covered" title="5 out of 5 forms covered">
-                147&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tree&nbsp;(simplify-rule&nbsp;(parse-rule&nbsp;rule))
+                147&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tree&nbsp;(simplify&nbsp;(parse-rule&nbsp;rule))
                 </span><br/>
 <span class="covered" title="9 out of 9 forms covered">
                 148&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;afn&nbsp;(if&nbsp;(rule?&nbsp;tree)&nbsp;(eval&nbsp;(generate&nbsp;tree))