change output file name (file path + name/stdout)

[mrghosti3]

Task is to add the argument for user to decide how to output the gcode:

• stdout (option is -);
• to a file with given name (just path with file name at end);
• or default behaviour is just the same as input file with appended .gcode extension.

[mrghosti3]

Decided the output should work like in curl:

• stdout (-) default;
• to a file with given name (just path with file name at end).