Added Address class

Because address field in user is insufficient, created class address.
It contains fields like country, zip_code, street, door_nr, house_nr.
It is converted to string automatically.
added address class and fixed adding sale to category
Merge branch 'feature/address' into develop
small changes in product
minor changes
changed on_discount percent to set_discount percent
before order changes
changed order to not point products to order_products. works, except for discount in order. need to add discount to order product, which will store discount of product at the moment of purchase
changes in specs, are a bit faster
refactored order ot use module total price and added persistency to order_product price and discount
joining products and categories is more efficient
some small changes in models, not important
fixed the discount price in product presenter bug
Merge branch 'feature/refactoring_changes' into develop
cleaning views
refactored all views, kinda works
sth
added favicon
before changes
Merge branch 'feature/refactoring_views' into develop