Generate an index ordered by reverse date with links to each file.

I would like functionality to easily move chronologically between notes
both forwards and backwards in time. This functionality is very similar
to that of VimWiki, although I think the default key bindings could be
improved.

Something to do with the conceal feature. I know it is implemented in other places, I just have to find out where.

Have sub level headings to group by year and/or month in the index. I would like to include a threshold, maybe 5, which if not reached will not group by month, instead just skip to year.

I will want to test at least python 3.5 and python 3.6, (also 3.7 if it is released before I get around to this). I don't think I have implemented anything that is python 3.6 only at this stage.

Commands only for files in these projects, i.e. not any other markdown files.

Command to copy external file to the log and create a link to the file in the logbook. This should handle text and image files in a sensible way. Include the image inline, while text documents can be a link, ideally also to a markdown document.

Pandoc flavored markdown has an anchor syntax which includes an anchor tag of the form {#}. This should be ignored when generating headers for the index file.

There should be no difference between searching a single file and all the files, with searches going to previous files.

Establishing the next and previous files is not working at the end of the list, in particular when
the latest file is yet to be saved. Basically files are getting skipped for some reason.