Spec: Minor cleanup in Appendix A

Spec: Document access conventions per opcode

Tweak spec language

Rewrite spec (#2)

Clean up documentation of baroque opcodes LOOKUP and EXTRACT

Clean up spec

Clean up FMTREAL helpers

STRCMP->KEYCMP in tests

Rename STRCMP opcode, which is not a simple string comparison, to KEYCMP

Cleaning up the VM spec

Remove duplicate method

Fix opcode names

Added doc/vm-specification.md

Implemented opcode 0x5F 0x35 as PRSREAL.

Implemented extended opcodes 0x31 (PINM) and 0x32 (UNPINM)