removing problematic classes on epub import, for cleaner pdf export

Two things in this commit related to epub import, which resolve some weirdness/duplication on re-exporting a PB generated EPUB — all attributes removed on import are re-created on export.

1. I've expanded what is considered to be a PressBooks generated EPUB, included those EPUBs made with 'secret sauce'
2. I've expanded the list of replacements, to include more attributes that will be affected by export stylesheets.