#109 Add trace command to debugger

[Witold Filipczyk]

trace would be similar to break, but instead of break, it could write message to stdout and continue running.
br{eakpoint} [something]
tr{ace} [something] [message]

Where something is the same as for breakpoint.
message could output variables, like registers, value from given memory address, and strings.
For example:
trace 2000 HL=$HL Mem $MEM[1400] $MEM[$PC - 10]
etc.

What do you think?