Add Apple II J-Plus support

[tomcw]

Now that custom ROMs can be loaded (#771), then I thought that J-Plus support (from the command line) was done, eg:

AppleWin.exe -model apple2p -rom IIJPLUS.ROM -videorom JVIDEO.ROM

But @sicklittlemonkey told me that the video rom (in AppleWin 1.29.11.0) isn't quite correct...

I did give it a go, though I wonder where that ROM
collection came from. I wrote the text files, but those ones are
different from the ones I remember releasing, unless there were
multiple versions. The full versions are here:
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Computers/Apple%20II/Apple%20II%20j-plus/Documentation/

Searching around I did find a problem with what I've written, and the
j-plus video ROM doesn't behave exactly as I would expect in AppleWin:
https://mametesters.org/view.php?id=6175

I don't have my original notes handy, but from memory I was going by
screenshots like the one at the link above (in fact possibly that
exact one) ...

It would be nice to get this working as it should.

Here's what AppleWin 1.29.11.0 shows...

From Nick's notes:

Characters in ROM:
00-3F Katakana } 00-7F activated by access to $C05C (annunciator 2 off)
40-7F ASCII    }
80-BF ASCII    ] 80-FF activated by access to $C05D (annunciator 2 on, set after reset)
C0-FF ASCII    ]

Characters displayed onscreen with annunciator 2 off:
00-3F Katakana - normal
40-7F Katakana - flashing
80-BF ASCII    - normal
C0-FF ASCII    - normal

Characters displayed onscreen with annunciator 2 on:
00-3F ASCII    - inverse
40-7F ASCII    - flashing
80-BF ASCII    - normal
C0-FF ASCII    - normal

So AN2 controls what video rom chars are displayed for 00-7F.
EDIT: NB. there's no way to get INVERSE Katakana.

To do:

• Add a new Apple II J-Plus model (apple2jp) to the code base
• Support AN2 just for this apple2jp model
• Expose this via cmd line & Config UI

[sicklittlemonkey]

Just a note that we verified the flashing behaviour. Here's a photo where it's caught changing.

[tomcw]

Added test: AppleWin/AppleWin-Test@2de648b

[tomcw]

Closing, as all complete with Help docs updated at db373c6