Refactoring tasks + datasets

• "Tasks & Datasets" tab should be renamed to "Resources"
• Tasks require "unit_test" / "solution" and a compute worker run is automatically ran when created

It should not be possible to:

• Edit or delete a file used by a task or an algorithm
• Delete a task used in a competition
• Delete an algorithm that was submitted to a competition
• Publish a task not validated by an algorithm
• Publish an algorithm not validated by a task
• It should be possible to delete multiple files at the same time.