Fix the datalink #doi entry

[kimakan]

This PR changes the description of the datalink entruies with the semantic #doi. Instead of The Digital Object Identifier for the ..., it will use the title of the table/schema obtained from the metadata. It is clear that it refers to the DOI of the given object due to the used semantic #doi anyway, thus the explicit mentioning of the DOI in the description is obsolete.
This change is due to the fact that the OAI-PMH interface uses the description of the #doi entry as title for the OAI record. It's wrong since the OAI record refers to the object itself and not to the DOI.

Optional tasks:

• add the description page for the custom semantics (currently #doi only)
• in the datalink viewer, resolve the semantics as links to the description

[coveralls]

Pull Request Test Coverage Report for Build 7286872818

• 4 of 21 (19.05%) changed or added relevant lines in 4 files are covered.
• 6 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.08%) to 63.873%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
daiquiri/datalink/views.py	2	5	40.0%
daiquiri/datalink/adapter.py	0	14	0.0%

Files with Coverage Reduction	New Missed Lines	%
daiquiri/datalink/views.py	1	55.56%
daiquiri/datalink/adapter.py	5	38.64%

Totals
Change from base Build 6612724739:	-0.08%
Covered Lines:	4779
Relevant Lines:	7482

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💛 - Coveralls