Implement "hide cursor" escape codes

These escape codes are used by programs that are doing full screen repaints, to
avoid confusing the user.

Signed-off-by: Morten Hustveit <mortehu@google.com>
Make cursor more visible

Use bright white background when window is focused, and don't hide it
completely when the window is blurred.

Signed-off-by: Morten Hustveit <mortehu@google.com>
Merge branch 'master' of github.com:mortehu/cantera-term