updated Makefile
updated sources.cfg
added doc for effects.
added more doc.
- commented subty (not used anywhere);
- compatible should allow any object targets.
merged the shared case and unique/0 case for effects2output in conversion.elf
added nat+map2map and set+map2map.
initial commit
added nat+map2map-implies-nat+set2set, and set+map2map-implies-set+set2set.
simplified definition for reftype/effects and re-proved read/write