[doc] Add more string examples
Track native get/set on hashes
[core] native_operations -> number_native_operations
[parser] Track type for _dummy_ variable
[core] Accept Lua string keys in hash.get/set/new
[parser] Allow Lua strings a hash keys

and optimize when hash is accessed by string literal
[parser] Fix more type tracking
[tests] Add more hash tests
Whitespace cleanup in parser