Fully documented MurmurHash3.

This attempts no code changes.

The highly modified class passes the current tests.

mvn clirr:clirr report shows no changes.
Default mvn goal passes:
mvn clean verify apache-rat:check clirr:check javadoc:javadoc

- Documented all public constants.
- Documented IncrementalHash32 class.
- Added <p> tags to paragraphs.
- Renamed input variables for consistency across all method.
- Renamed internal variables in the hash32, 64, 128 methods so the
similarities in the methods are obvious.
- prefix joavadoc @params and @returns with 'The' consistently
- Added code examples for the methods that hash primitives for the
equivalent using a ByteBuffer to encode the bytes.
- Fix links in the class header.
- Documented sign extension bugs in hash32 and hash128.
- Documented hash64 is not from the reference code and does not match
part of hash128.
- Documented hash64 as may be released in a future version.
- Refactored combination of bytes to little endian int/long into
methods.

Author: aherbert