Greatly improved VT100 compatibility.

Used the vttest tool to improve support of VT100 escape sequences:

* Fixed incorrect behaviour of the "ESC [ Ps J" and "ESC [ Ps K"
  escape sequences.
* Fixed terminal breaking on escape sequences containing numbers with
  leading zeros.
* Fixed terminal ignoring control characters inside of escape sequences.
* Fixed incorrect behaviour of autowrap.
* Added ability to toggle DEC autowrap (DECAWM).
* Added support for DEC screen alignment test (DECALN).
* Added support for 80-column and 132-column mode (DECCOLM).
* Added support for origin mode (DECOM).
* Added support for tab stops, and dynamically setting and resetting tab stops
  through control sequences.
* Added support for G0 and G1 character sets, rather than just G0 as before.
* Cursor position-saving control sequences now also save colours and other
  attributes created by "ESC [ Pm m" as well as the current character sets,
  as they are supposed to.
* Added partial support for full-screen reverse video (DECSCNM).
  By default, the terminal uses a fast version of reverse video for
  performance reasons. To use full reverse video, use the terminal's
  setFastReverseVideo(false) method.