SamSequenceRecord implements Locatable

[lindenb]

Description

This PR only makes the coding easier.

I often find myself testing if a Locatable overlaps a SamSequenceRecord .

interval.overlaps(new Interval(ssr.getSequenceName(),1,ssr.getSequenceLength()));

This PR adds the interface 'Locatable' to SamSequenceRecord (with start=1 && end=sequenceLength()).

interval.overlaps(ssr);

Things to think about before submitting:

• [X] Make sure your changes compile and new tests pass locally.
• [X] Add new tests or update existing ones:
  • A bug fix should include a test that previously would have failed and passes now.
  • New features should come with new tests that exercise and validate the new functionality.
• [ ] Extended the README / documentation, if necessary
• [X] Check your code style.
• [ ] Write a clear commit title and message
  • The commit message should describe what changed and is targeted at htsjdk developers
  • Breaking changes should be mentioned in the commit message.