Fix invalid context check warnings

[Pfeil]

• Handle @id as type as if the id would be the type.
• Consider @json to be a type which does not need context. Consider making a list in case we discover more such cases later on.
• make sure something like https://schema.org/Dataset is handled properly as a type and not as a suffix of a type (see below). We might need some proper types abstraction for this.
• tests missing

[coveralls]

Pull Request Test Coverage Report for Build #252

Details

• 11 of 11 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.04%) to 90.687%

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Totals
Change from base Build #249:	0.04%
Covered Lines:	1597
Relevant Lines:	1761

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💛 - Coveralls