st1206: implement Local set for SAR motion imagery

[bradh]

Motivation and Context

This is a ST0601 nested local set that we don't currently support.

Resolves #166
Relates #198

Description

Full implementation of ST 1206.1
Also implement ST 1403.2 SARMI Minimum Metadata validation. That is useful because the test tools don't check this part completely.
Also added SARMI to generator example. There are some minor cleanups mixed into that, because I got a new CMITT which showed new problems during test.
Includes initial work on ST 1303 for floating point values. That in turn required extensions to the PrimitiveConverter code, which also got some more unit tests for existing code.

How Has This Been Tested?

There is no public / releasable test data that I know of - asked MISB, but not expecting a positive answer.
I did extend the generator example to output SAR Motion Imagery metadata, and pushed that through CMITT. It passes, but I don't think CMITT is checking all the values, so that is of limited confidence. Better than nothing though.
There is good unit test coverage.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.