Dataset: Add technical resource input

[ValentinFutterer]

Description
See the backend issue for context. Users should be able to put in technical resources for new datasets, but not reused ones. A dataset can have multiple technical resources. A technical resource has a name and a description attribute, but only the name is required for our purposes, since this way its kept more userfriendly. (So you dont need the description input and null can be sent to the backend for description - I discussed this with Tomasz) Name input should be a textarea though, since user might want to put in multiple lines, but with a 255 character limit.

For wordig an dhelptext, consult the common standard and or Christiane/Tomasz.

Additionally, you have to solve the size problem here, the table is already dangerously small, especially with multiple technical resources:

Maybe add a menu point that shows additional info on demand, and only show the most relevant points per dataset in the table? Other ideas are also welcome.