attribute_type data definition and properties

[andrixnet]

Attribute type defines the kind of attributes of a cache. Each attribute type is identified by a unique ID.

Properties:

• ID
• name (for referencing translations)
• base image icon
• category (new; eg dangers, requirements, etc)

[kojoty]

I don't understand what needs to be done here. Can anyone clarify it?

[following5]

Suggest to merge this to #462. It's mostly redundant.

[andrixnet]

@kojoty this and similar issues I created to describe enhancements towards well defined data structures.
In particular, this lists a potential enhancement to atributes, that is categorization.

Also serve as a template for defining this data in the code (since part of it stil resides in database tables)