parallelise making stances

and document the process of running them slightly better
parallelise make_mp_stances

And display all errors at the end, in case you don’t see them in the
wall of text
New stance data

recalculated MP and Party stances after fixing PW parsing bug
Don't show scores for stances

Now that we’ve fixed most of the bugs, don’t display the stance scores.
Independents

until we come up with a better way of handling Independent MPs, at
least call their “party” Independent*s*, so that it scans better.
remove link text from issues

As it clobbers linking to the Issue page