Scale images to fit the page for DOCX

Images that are bigger than the page were truncated. This will now
scale them if they are larger than the page. The scale is currently
hardcoded with Word "letter" defaults (page size and margins)
Docx reader: Add test

Test auto ident header anchors with pandoc-generated pandoc.
Shared.fetchItem:  unescape URI encoding before reading local file.

Close #1427.
Require highlighting-kate 0.5.8.4.

For correct highlighting of identifiers in prolog and other languages.
EPUB writer:  Keep newlines between block elements.

This allows easier diff-ability.  Closes #1424.
LaTeX writer: Use \nolinkurl in email autolinks.

This allows them to be styled using `\urlstyle{tt}`.

Thanks to Ulrike Fischer for the solution.
HTML writer:  Removed useless clause.
Docx Reader: Change state handling.

We don't need `updateDState` -- the built-in `modify` works just
fine. And we redefine `withDState` to use modify.
Docx Reader: Fix hdr auto-id when already auto-id.

If header anchors (bookmarks in a header paragraph) already have an
auto-id, which will happen if they're generated by pandoc, we don't want
to rename it twice, and thus end up with an unnecessary number at the
end. So we add a state value to check if we're in a header. If we are,
we don't rename the bookmark -- wait until we rename it in our header
handling.
Merge pull request #1430 from jkr/anchor-fix-2

Fix auto identified headers when already auto-id'ed
Removed redundant clause in markdown parser.

Thanks @dubiousjim.  Close #1431.
Made Citation information available in lua custom writer.
Updated changelog.
Custom writers now work with `--template`.

Removed HTML header scaffolding from data/sample.lua.
Remove unused import.
Org reader: Respect :exports header arguments on code blocks

Adds support to the org reader for conditionally exporting either the code block,
results block immediately following, both, or neither, depending on the value
of the `:exports` header argument. If no such argument is supplied, the default
org behavior (for most languages) of exporting code is used.
Merge pull request #1435 from bosmacs/org-babel-exports

Org reader: Respect :exports header arguments on code blocks
Fixed typo in link
Renamed readTeXMath' to avoid name conflict with texmath 0.6.7

Also removed deprecated readTeXMath.
Require highlighting-kate >= 0.5.8.5.