Improve console UI

This one would be pretty easy for somebody to help with.

The current console UI kind of sucks: it's just a giant div that we stuff text in. We should try to use a terminal emulator.

• text will wrap properly
• we can autoscroll to the bottom better
• probably won't lag during an ios build, when tons of text gets logged all at once (slowness might be due to other stuff)

This task is a prerequisite for being able to type back into the console (currently is read-only), and being able to search console output.

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How to improve it?

Consider using https://github.com/sourcelair/xterm.js, the actively maintained fork of termjs.

This should fix text-wrapping, scrolling, and probably performance (although we may also want to batch text output into the console). It will set us up to be able to run commands via the console and search console output.