Interpolate console animation, Make con_height update on the fly

Interpolates the console's openining/closing animation, and makes it no longer be affected by timescale.
As a related bonus, the con_height console variable now takes effect immediately, without requiring you to close and re-open the console.
As a bonus related to that bonus, the input text prompt is now displayed while the console is moving, not only when it's reached its destination.

Fixes #905 (closed)'s feasibly-fixable thing.

TL;DR:
- Interpolates the console
- con_height now updates on the fly