Minor reorganization of sectioning
Minor reorganization of sectioning

Upgraded a level 4 section to level 3, since it was the only one and
there was no more text. Refs #2063.

MasterDuke17/doc,jonathanstowe/doc,dmaestro/doc,stmuk/doc,dmaestro/doc,perl6/doc,perl6/doc,perl6/doc,stmuk/doc,jonathanstowe/doc,stmuk/doc,perl6/doc,MasterDuke17/doc,tbrowder/doc,tbrowder/doc,MasterDuke17/doc,perl6/doc,stmuk/doc,dmaestro/doc,jonathanstowe/doc,tbrowder/doc,MasterDuke17/doc,jonathanstowe/doc,jonathanstowe/doc,tbrowder/doc,stmuk/doc,dmaestro/doc,dmaestro/doc