MIME cleanup.

  * Create a type synonym for MIME type (instead of `String`).
  * Add `getMimeTypeDef` function.
  * Avoid recreating MIME type `Map`s every time.
  * Move “Formula-...” case handling into `getMimeType`.
Update Reader.EPUB to use `MimeType`.
Remove an unnecessary import.
LaTeX writer: Use a declaration for tight lists

Currently, pandoc has hard-coded the following in order to make tight lists in
LaTeX:

```hs
text "\\itemsep1pt\\parskip0pt\\parsep0pt"
```

Which is fine, but does not allow customizations.  For example, the `memoir`
class already has a `\tightlist` declaration for this purpose:

```tex
\newcommand{\tightlist}{%
  \setlength{\itemsep}{0pt}\setlength{\parskip}{0pt}}
```

I'm proposing to use a similar solution:

```diff
@@ In Writers/LaTeX.hs:
-then text "\\itemsep1pt\\parskip0pt\\parsep0pt"
+then text "\\tightlist"

@@ In templates/default.latex:
+\newcommand{\tightlist}{%
+  \setlength{\itemsep}{1pt}\setlength{\parskip}{0pt}\setlength{\parsep}{0pt}}
```

This allows us to customize the tightness to our needs.

If a person is using a custom LaTeX template (not based upon the `memoir`
class), the `\tightlist` declaration must be added.
DokuWiki writer: Use backslash newlines in table cells.

Write out strings in table cells with backslash linebreaks in place of
newlines. We also want to remove the first two spaces of an indent in lists.
Removed extra blank line after version.
Merge pull request #1580 from jkr/stringCellDokuWiki

DokuWiki writer: Backslash newlines in table cells
Updated README on `--self-contained`.

Removed outdated claim that pandoc will look in the user data
directory if a relative path is specified and the file is not
found locally.  Closes #1572.
Updated changelog.
Merge branch 'mime' of https://github.com/Aelve/John into Aelve-mime

Conflicts:
	src/Text/Pandoc/Writers/Docx.hs
Updated changelog.
Dokuwiki writer: Add a test for multiblock table cells.

We have to add a new file, because the original table tests don't look
for this.
Added new dokuwiki multiblock table tests to pandoc.cabal.
Makefile: Fixed install target to use copy, register.

This way the last configuration is used.
Version bump to 1.13.1.
Updated README date
Makefile:  Add README as dependency of man pages.
Put version in lower-left corner of man pages.
PDF:  Catch errors in conversion of images and display message.

See #1582.
Textile reader: Improved table support.

We can now handle all different alignment types, for simple
tables only (no captions, no relative widths, cell contents just
plain inlines).  Other tables are still handled using raw HTML.

Addresses #1585 as far as it can be addresssed, I believe.