Better slash commands, and console printing

Improve the slash commands, so `/lua` will evaluate expressions, and `/dump` will inspect them.

Update the console support to define a `print()` for expressions to print to the console (only while evaluating code in the console), and make `inspect` work like `/dump`.
Ugh, sorry about the whitespace changes. Houston is not a very good editor (granted, I'm thrilled it exists at all, but its text editing behavior leaves a lot to be desired). I can clean this up if you want.