Moved `MediaBag` definition and functions from Shared:
`lookupMedia`, `mediaDirectory`, `insertMedia`, `extractMediaBag`.
Removed `emptyMediaBag`; use `mempty` instead, since `MediaBag`
is a Monoid.
This will make paragraphs styled with `Author`, `Title`, `Subtitle`,
`Date`, and `Abstract` into pandoc metavalues, rather than text. The
implementation only takes those elements from the beginning of the
document (ignoring empty paragraphs).
Multiple paragraphs in the `Author` style will be made into a metaList,
one paragraph per item. Hard linebreaks (shift-return) in the paragraph
will be maintained, and can be used for institution, email, etc.
We want to treat it as a plain paragraph if the hanging amount is
greater to or equal to the left indent---i.e., if the first line has
zero indentation. But we still want it to be a block quote if it starts
to the right of the margin. Someone might format verse with wrapping
lines with a hanging indent, for example.
This is what seems like the sensible default: read in insertions, and
ignore deletions. In the future, it would be good if options were
available for either taking in deletions or keeping both in some
scriptable format.
Add torture-test for new normalization functions.
One problem that this test demonstrates is that word has a tendency to
turn off formatting at a space, and then turn it back on after. I'm not
sure yet whether this is something we should fix.
This is just a wrapper around Pandoc that doesn't normalize with
`toString`. We want to make sure that our own normalization process
works. If, in the future, we are able to hook into the builder's
normalization, this will be removed.
