Renamed poly to letv.
Reorganized files.
Wrote comments for names.elf
Renamed operation to opsym.
Introduced operations as pairs of instances and opsyms.
Cleaned up "effects.elf".
Cleaned up effects-lemmas.elf
Cleaned up terms.elf
Cleaned up types.elf
Cleaned up types-lemmas
Cleaned up typing.elf.
Cleaned up typing-lemmas.elf
Cleaned up operational.elf
Cleaned up big-to-small.elf and small-to-big.elf