EB

The primary readline interface has been redone using the excellent prompt-toolkit.
This is pure Python code so it should be available everywhere.
We still include GNU-Readline for those situations where prompt-toolkit doesn't work. Select the readline style now with the
--choice option which can be one of GNU, Prompt, or None.

Prompt toolkit allows us to color input as it is getting typed. It also has nicer completion facilities, and sports a bottom modeline status bar.

There is still a bit of cleanup work to do to support GNU readline inputrc files better, or to handle completion better, but this will come later.

Independent of prompt-toolkit, there better pygments colorization using mathics-pygments. Expect that to improve over time too.