Issue 3781 Directions for posting should change depending on selected editor

http://code.google.com/p/otwarchive/issues/detail?id=3781

When posting a work, chapter, known issue, admin post, or archive FAQ section, you can toggle between the RTE and the HTML editor. The directions "Plain text with limited HTML" should appear when the HTML editor is selected and "Type or paste formatted text" should appear when the RTE is selected.

Main changes in the first commit:
* Moved the jQuery for toggling the RTE and HTML editor and instructions into the RTE's JavaScript file so it can be reused instead of repeating it on every page those editors are included
* Stopped using spans for the RTE and HTML editor and their instructions and started using mark-up more consistent with the rest of our code (the buttons are in a `ul` with `role="menu"` and the instructions are wrapped inside a `p`)

Secondary changes in additional commits (commits done by file for your reviewing pleasure):
* Indent fixes on the known issue, archive FAQ, and admin post forms
* Moved the admin post notice about required fields inside the form, which is the desired location
* Made strings in the admin post and archive FAQ forms translatable
* Corrected some misleading form IDs (known issues, admin post, and archive FAQ were all using the ID "work-form" despite not being work forms)
* Closed a `<div>` in the archive FAQ form