feat(core): create @skele/core package

[andon]

The @skele/core package contains the following features (usable from all supported environments):

• data, registry, zip
• logging internals

It's mostly extracting it from @skele/classic with using it as a dependency in there, while preserving the same API.

More details about the new package restructuring: #99

[coveralls]

Pull Request Test Coverage Report for Build 345

• 27 of 27 (100.0%) changed or added relevant lines in 16 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.003%) to 78.389%

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Totals
Change from base Build 344:	1.003%
Covered Lines:	862
Relevant Lines:	1028

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💛 - Coveralls

[ognen]

Just, move propNames also into core as the element zipper and various data fns depend on these names.