Link from partner admin page to species editor

For #376, we now print a little summary on a partner object's admin page
showing how many species it has, next to a link to where you can edit
them.
Add edit page listing species for a partner #376
Allow botanist download of partner-site species

It is delivered as a plain CSV file. #376
Refactor generation of partner-species CSV rows

The actual row generation is now the job of a separate class, which will
soon be in charge of the actual insertion and deletion of the real
database records behind the rows. #376
Rename a page template from "edit..." to "view..."

The view is not actually used for editing, and we might need the "edit"
name free for a page that actually does support inline editing. #376
Move /partner-plants/N/ to /partner/N/plants/ #376

This creates a URL prefix "/partner/N/" that will be more amendable to
the creation of further pages as events may warrant.
Switch to "tablib" since it supports Unicode CSVs

On the way to resolving #376.
Correct how we compare plant-list tuples #376
Support for CSV upload of partner plant lists #376

This needs refactoring and makes me feel like we are missing a lot of
basic business-logic abstraction.  My views are full of raw database row
manipulation instead of clean assertions about what state things should
be in at the level of information.  But, the new form and logic at least
seem to work.
Merge branch 'partner-species-upload'

This achieves most of #376 by adding the ability to upload and download
CSV files of partner-site plant lists.