Consider environments / servers

Currently, the website is configured to always retrieve its data from the TextAPI at eupt-dev.sub.uni-goettingen.de. This should not be hard-coded, but depend on the server we're serving the website.

• eupt.uni-goettingen.de --> eupt.uni-goettingen.de/api/eupt/collection.json
• eupt-dev.sub.uni-goettingen.de --> eupt-dev.sub.uni-goettingen.de/api/eupt/collection.json
• eupt-test.sub.uni-goettingen.de --> eupt-test.sub.uni-goettingen.de/api/eupt/collection.json