Switch to using floating nuget version numbers

[CBielstein]

Description

As per the Microsoft nuget best practices document, this project should update to use floating versions rather than specific versions on the libraries being published to nuget.

I'm a bit skeptical about their guidance to not use upper bounds, as a new major version implies breaking changes under semantic versioning, so perhaps we just switch to locking to a major version.

Acceptance Criteria

• Nuget dependencies in nuget-published libraries (KissTnc, AprsParser, and AprsIsClient) should be floating versions, not locked