nec/pc6001.cpp: Add cassette software lists

[paul75s]

2nd attempt - enables 2 new software lists:

pc6001_cass, supporting all PC-6001 models (with 16 initial working software items)
pc6001mk2_cass, supporting PC-6001mkII, PC-6001mkIISR and PC-6601 (with 18 initial working items)
Approach of separate software lists, with each treated as original is consistent with approach for pc8001 and seems appropriate due to PC-6001 software being fully supported on later versions, and PC-6001 software often having mkII modes.

In line with the current hack to enable cassette based software, items are configured as carts, not cassettes.

All software items sourced from TOSEC repositories.

Revisions from initial attempt at this:

• All items flagged as partially supported. This seems appropriate based on the software largely/fully functioning but requiring the current hacks to support cassette based software. Happy to modify to not supported though if this seems more accurate.
• Fixed missing tag in pc6001_cass.
• Corrected a couple of game names and also amended/enhanced some metadata, including addition of alternate Japanese titles where I can find these.

Where included files are in .p6 format, these are working (along with .cas files).