Add methods to add/remove categories and to get/modify website branding

Categories
 - POST {HOST}/rest/product/category/(NAME}
 - DELETE (HOST}/rest/product/category/{CATEGORY_ID}
   - Requires ADMINISTRATOR role

 Branding
 - GET {HOST}/rest/brand
 - POST {HOST/rest/brand[?[title={NEW_TITLE}]&[slogan={NEW_SLOGAN}]]
   - Requires ADMINISTRATOR role