Add support for erase-in-display codes with numbers other than 0.

[gbmhunter]

Especially useful would be support for "2", which clears the screen.

[gbmhunter]

Erase in display 2 (<ESC>[2J ) is clearing the whole screen. This should clear the whole screen, move the cursor to home (top-left) but leave the scrollback buffer.

Would have to delete all chars from rows below the cursor but leave the rows there, otherwise it would be impossible to scroll so that the cursor is in the top-left.