Fixed Admin # Products # Index,Form,Show

Index:
- With a high variety of products, previous grid styling broke, in part
  due to the existence of very long names which caused the title to take
  more than one line.
+ Grid styling replaced with Bootstrap thumbnails.
+ Displayed product names limited to `maxlen`, currently hardcoded at
  10.

Form:
- With no brands to choose from, the warning in the products form was
  not properly aligned. Same happened with the prototypes.
+ Added styling specific for these warnings.

- Without any variant properties, the respective checklistbox is reduced
  to a grey line.
TODO: add a check to validate if any variant properties exist. Add the
	  same check for categories.

Show:
- Without any variants or properties, the show page of a product only
  showed the respective title for these fields.
+ Added conditional text to inform the user.