added more special keys

Key now supports Home, End, PageUp, PageDown, Delete, Insert and
Function keys. All this is done through the detection of both VT100
escape codes and more modern standard counterparts.
For instance, F2 can be both
    ESC OQ
on VT100, screen, and some versions of xterm and
    ESC [12~
on rxvt and other xterm versions depending on your terminal