Restructure products.

+ Replace former field with separate fields for
  vegetables, animal products, beverages and
  additional product information.
Hide product headline when empty.
Show descriptive product names in entry farm wizard.
Concatenate products displayed in map pop-up.

+ Disable logging for empty product groups.
Reduce number crunching code in view template.

+ Products array is translated at once when not empty.
Display products merged by farm.
Re-use functions to join products.

+ Disable logging for not existing product groups.
Merge branch 'feature/refactor-products-191' into prototype
Enable validation for "maximum members" attribute.
Merge branch 'feature/validation-maximum-members-191' into prototype
Calculate temporal word dependent on the foundation date of the farm.
Merge branch 'feature/dynamic-temporal-connection-word-191' into prototype