Issue #92 - Incorporate BCH code into AIT-DSN

[nttoole]

• Integrated ASU-source BCH utility into ait/dsn/bch
• Added unit tests for expected successful and rejected input
• Added basic sphinx documentation for BCH and associated tests

Resolves #92

[MJJoyce]

FYI, above changes were to fix a merge conflict in setup.py and fix the import structure in ait.dsn.bch to be python 3 compliant.