Implement FCOPY

[tschak909]

FCOPY needs to be implemented that implements the [C]opy function that is in CONFIG, as a tool that can be used outside of CONFIG.

You can use any of the F* or N* tools as a template to get any code you need.

How it needs to work:

FCOPY <source_host_slot>,<sourch_path>,<destination_host_slot>,<destination_path>

example:

D1:FCOPY 2,/some/path/to/file,1,/some/path/to/destination/file

The copy command is described here:
https://github.com/FujiNetWIFI/fujinet-platformio/wiki/SIO-Command-%24D8-Copy-File

and the code that config uses, is here:
https://github.com/FujiNetWIFI/fujinet-config/blob/master/src/diskulator_copy.c