Update highlight plugin configuration to support tabs

The technique we were using to configure the library was incorrect.
Provisionally make tag pill foreground colour be responsive

With this commit tag pills will now choose for the foreground colour
either the current palette “foreground” or “background” colours,
according to which has the higher contrast. It’s something @gernert has
expressed an interest in in the past, and I’ve tended to agree that it
is a nice piece of polish. It opens up the possibility of paler colours
for tag pills than are currently possible.

The trouble is that in order to implement it I’ve had to bring in a
third party library for parsing CSS colours. It weighs in just over
9KB, making quite a lot of weight for such a small feature. I don’t see
any other immediate uses for the colour parsing library either.

So, I’m undecided at the moment whether this should stay in the core.
Experiment with alternative view tiddler toolbar default buttons

The “info”, “edit”, “close” troika has been a feature of TW5 since the
very early days. Recent discussion in Hangout #67 has made me question
whether we wouldn’t be better off with the defaults in this commit:
“more”, “edit”, “close”.

The rationale is that the primary purpose of the “info” button has
become gaining access to the tools that haven’t been elevated to being
toolbar buttons. Most of the rest of the content of the info panel is
pretty arcane. So let’s try it for a few days - I’d appreciate any
feedback.