DRILL-4119: Modify hash32 functions to combine the msb and lsb bytes of a 64-bit hash value (previously, we were casting to integer).
- Use this new set of functions (for all data types) for creating the hash values needed for hash distribution, hash joins etc.
- Rename HashFunctions to Hash32Functions to be consistent with the Hash64 counterpart.
- Many data types did not have a hash32AsDouble equivalent...added these.
- Add hash32 functions with seed.
- Fix unit tests, add "hash" as a synonym for "hash32".
- Rename HashBigInt to BigIntHash everywhere to be consistent with other names.
close apache/drill#279
