Always use a sortedCompletion.

This is the DWIM API. You almost always M sorted. If you don't M sorted, then
use the more complex API.
Added clear-log.
Minor tweaks.
Moar libs!
Added invalidStyle.

This avoids the temptation to use warnStyle or errorStyle when styling syntax,
because that will cause problems when those two styles are not automatically
removed from restyled code.

I may have to rethink the style business (or the TextMate syntax to style
business) because that particular bear trap is pernicious.
Added showStyles(). For great debugging!
Move read-only buffer creation to Buffer.apply.

Other test code wants to create test buffers, and there's no harm in making
this widely available.
Provide Java executors for UI and BG running.