(Feature Request) Commandline text import

[Gumball2415]

[TheRealQuantam]

Have a first draft of an implementation for this at https://github.com/TheRealQuantam/Dn-FamiTracker/commit/a87ffbd29c0a918381c0325799ee36aad15e554f . It needs some executive decisions, e.g.

1. The syntax for the command line.and whether the command should be "import" or "convert". Initially I used "import", but I changed it to "convert" to leave "import" available for opening a TXT file from the command line into the GUI.
2. Where exactly the code should go
3. The variable names in the params struct to use (it's a bit weird so as to reuse an existing variable and not create a new one)