Move character selection logic from chr to one/two

[st3fan]

Currently chr builds up a character set for the Apple ][ with normal and inverse text. The Apple 1 uses the exact same. I think instead chr should just load characters from a ROM and keep those and the one and two can map those to actual ASCII tables. Then chr is independent and the machine specific logic will be in in the actual machine. This will also be good when we support the Apple IIe which has a very different character set.