Maintain/2 0 remove deprecations

[kroenlein]

This PR removes methods that were deprecated, scheduled for removal w/ the 2.0 release.

• Drop name argument from LinkByUID.from_entity
• Drop type-casting methods get_value and get_enum from BaseEnumeration
• Drop register_classes meta-method from GemdJson
• Drop native_uid argument from substitute_links from util

[anoto-moniz]

Why? I don't see anything else called json, and even if there was, I'd suggest aliasing the other thing rather than the built-in.

[kroenlein]

Originally done b/c I'm having some weird namespace collisions in my IDE, but this didn't fix it. However, there's enough weird use-built-in-for-some-stuff-but-custom-elsewhere in this library that until that gets cleaned up that I think it's important to be clear which is being used. Maybe I'll get it cleaned up next release. Or when we change techs.

[anoto-moniz]

LGTM. Just that one comment, but it's on a test file and not a big deal.

[anoto-moniz]

As noted in Slack, I'm very opposed to the renaming of the builtin json import on the basis of clarity, and even more since it's to cater to a specific IDE.

But as I also noted, I don't care enough to argue about it, so I won't block on it.