css changes, reorganised file directory, headings

Something went belly-up in terms of the repository existing on a USB
stick. I think this has been recovered from, but it sure-as-hell would
be easier if Windows didn't have stupd line-endings. I think from now
on, I'll make all commits from a Linux machine, after ensuring all files
have a trailing newline and have no CRLFs in them.

As for actual changes, we'll begin with CSS. I have slightly altered the
margins of the body and aside elements, giving the contents blist a bit
more breathing room below.

I have also reorganised the "file" directory, categorising each file
into one of a few sub-directories. I have updated index.php and any
concerned markdown documents accordingly.

As per usual, the headings handler class has changed too, and the
contents and headings processor are working as they should, at last. In
other class related news, the highlight class is gone, as realistically
there would be no point developing it further, and I had no real desire
to. The markers are just going to have to deal with boring mono-shaded
code.

I have also added a new "ext" document, as part of 1.2. This partly
prompted the additions to index.php, which make it list an "ext"
markdown in the main page, as opposed to just the main documents.

The next commit will likely involve tidying up Windows' mess and will
mark the start of a new era of repository management etiquette. On the
downside, I'll have less reason to slag off Microsoft then.