Add support for C16, C116, Plus/4 computers

[Esshahn]

Support for those computers should be straight forward:

• different color palette
• different addresses in assembly export
• slightly different BASIC exporter

Good starting point could be to analyze Marq's handling of the plus/4 format in terms of colors. I would happily provide the BASIC exporter.

[nurpax]

Makes sense for orthogonality but probably will not go intonthe next releasr line. :)

[Esshahn]

Some quick observations: Colors are incremental from top left to bottom right:

Gives values for colram in .c file

So with changed values for col and screen ram in the BASIC code

20 poke 65305,6
30 poke 65301,0
100 for i = 3072 to 3072 + 999
110 read a: poke i,a: next i
120 for i = 2048 to 2048 + 999
130 read a: poke i,a: next i

the current BASIC exporter does already work on C16/ Plus/4 (color values are wrong of course)