Lua console improvements

[GinjaNinja32]

Scroll text to fit rect if there is a gap that could be filled

If there is empty space at the bottom of a multiline text box, and the text also goes off the top, move it down until one of those two things is no longer true. Prevents a weird edge case where the (closed) console shows a small number of actual lines, while showing a much larger background box.

(I'm still not sure how it gets into that state, since it seems to be able to scroll fine most of the time; regardless, this makes it fix itself and display as much text as possible whenever it would otherwise not do that)

Render text starting at same y whether console is open or closed

Simple one; replace the 15 + lines*15 with (0.3 + lines) * linespace to match the positioning when the console is open.

Disable text box when console closed

This makes the closed console visual-only, with no click interaction; the open console captures clicks and prevents click-through as before. Enables server interaction with the top half of the screen even if the console is noisy.