Renamed RAM to MAIN for all disk based targets.

Renamed RAM to MAIN for all disk based targets.

The name RAM doesn't make much sense in general for a memeory area because i.e. the zero page is for sure RAM but is not part of the memory area named RAM.

For disk based targets it makes sense to put the disk file more into focus and here MAIN means the main part of the file - in contrast to some header.

Only for ROM based targets the name RAM is kept as it makes sense to focus on the difference between RAM and ROM.