This polishes up the Markdown links for the various edit fields. They're

now blue and don't have an underline, and they're also much shorter.

Particularly for the comment dialog, where it was taking up valuable

space and making it harder to drag the window.
For the comment dialog, the text is now just "Markdown." For the other

fields, where we have room, it's "Markdown Reference."
This also cleans up the code a bit to put the links in the templates

instead of injecting them into the DOM elsewhere. For comment dialogs,

it's in the template now (and no longer displays when showing the

"you must log in" or "it's a draft!" messages). For the inlineEditors,

it's now MarkdownEditorView that sets it up and not each individual

instance.
The root of the user manual is now a main JavaScript constant instead of

repeated throughout the codebase, making it easier to maintain. Each of

these links reference it.
There's also some fixes for the links in the comment dialog, which

weren't pointing to valid addresses.

Tested that all the links worked.
Checked every instance, and made sure that the MarkdownEditorView-initiated

ones weren't showing up in places they shouldn't.
Tested the comment dialog when logged out, and when on a draft.
JS unit tests pass.