Visual Editor

This editor, unlike the Block Editor (B100), is grid-based
instead of being command-based. It requires the AT-XY, COLS
and LINES words to be implemented. If you don't have those,
use the Block Editor.

It is loaded with "125 LOAD" and invoked with "VE". Note that
this also fully loads the Block Editor.

This editor uses 19 lines. The top line is the status line and
it's followed by 2 lines showing the contents of IBUF and
FBUF (see B100). There are then 16 contents lines. The contents
shown is that of the currently selected block.

                                                        (cont.)
