Harness start invocation should send entire time value

[jasonmlkang]

Included in this PR:

• [x] send entire time value in raf.py and rcf.py

Refs:

• Original ticket: #138

[jasonmlkang]

@jasonmlkang Could we wrap the new code as a common method that takes a time, and optionally an offset (which defaults to the CCSDS_EPOCH)?

Done in e58784d

[jasonmlkang]

@nttoole Unit tests add in 9b3b9dd. PR is ready for review.