Documentation update

Rework for Doxygen >1.8. Moved large parts of the documentation to a
simplified format, making use of Markdown enhancements and fixing bad
long options.
Added some clutter

Subllime and a few temporary files.
Removed dupes from gitignore
Simplify styling
Merged in latest changes to docs and formatting tweaks

Addresses issue #1557 as well as fixing many typos, HTML errors and
inconsistencies. Also introduces automatic syntax colouring and enables
new documentation to be written in Markdown. TODO fix Tutorial.
Fixes lexicon filter pipes '|"
Style fix for sub-line comments
Lexicon filter: fix 'if' and 'for' special cases
Add lexicon filter to manpages.

 Fixed manpage 'NAME'. Under Doxygen 1.8, the output format has
changed, so the old sed script was leaving man pages with two titles.
Fix missed escaped '--' inside /fish block
Update autoconf and README for Doxygen 1.8
Revert Xcode project

This reverts accidentally included files in commit
60b9f8db18b8889c3db864e443ee113d897bfe72.
Revert 60b9f8d..e4d6eaf

This rolls back to commit 60b9f8db18b8889c3db864e443ee113d897bfe72.
Update configure.ac and README for Doxygen 1.8
Updated build_doc…sh to run cleanly in Xcode build

If the lexicon input filter isn't specified (as is the case in the
current Xcode project, the script quietly continues without it.
Tutorial auto colouring, Man page and Make fixes

Completely fixes #1557 and the underlying Doxygen changes that caused
it. Should make fish docs simpler and more robust, more consistent and
generally prettier.

todo:
- trap unmarked text as arguments in context
- test & fix sed portability - see in particular. (so far tested on BSD
(Mac) and GNU sed).
- test Makefile changes
- last round of aesthetic changes and getting that ascii fish in there…
Fix ampersand redirector
Fix trailing backslash after complex options
Fixed a few more edge cases
gitignore changes