Don't allow arbitrary headers

Revert "Allow arbitrary headers"

I'm thinking of prose manuscripts.  Screenplays, and presumably comic
book scripts, don't have the name of the work on every page.  They
have three holes with brass tacks going through them.

This reverts commit 1edce1177b99d1637fe9e3badf290b7e7fd747c8.
Change headers from "PAGE n" to "n."
Hollywood seems to count pages starting at 0
Screenplay title pages are just that
Number pages starting with "2."