Initial work towards BIP0037 bloom filtering API.
Cleanup and finish BIP0037 bloom filter API.

This commit finishes the work started by @dajohi on bloom filters.

- Rename the package from bloomfilter to bloom
- Rename New function to NewFiler
- Rename Load function to LoadFilter
- Rename BloomFilter type to Filter
- Rename Contains to Matches
- Correct tx match handling to match all inputs and outputs instead of
  only the first one
- Optimize murmur hash function by using constants
- Optimize the merkle block creation and reduce num of memory allocations
  required
- Make MsgFilterLoad concurrent safe as intended
- Update various code consistency issues
- Add a lot of comments
- Improve tests
- Make the code golint clean