Implement command history feature

[joemcool]

I'd like to implement a command history feature. I imagine it would work similarly to other command shells, where the up and down arrow keys cycle through recently used commands. The user would have the option of making changes to a previous command's arguments before running it again. This may also lead to implementing the left and right arrow keys, allowing the user to move a cursor left and right when typing a command.

I expect this feature will require a significant amount of memory to be used, around 700 bytes for a 10 item long history list. This much memory usage only makes sense on larger modules (Arduino Mega, ESP8266, etc.), so this feature should be disabled by default and enabled via a macro in the Shell.h file.

I'm happy to implement this feature myself, but I'm curious if the community has input on how this feature would work?