Tidy up model loading

[adampatterson]

There is a lot of duplicate code loading models in various controllers.

Clean this up by moving references to class properties, and further on into the properties helper if it will work.

[adampatterson]

Moving models to a centra location doesn't help to clean up the code as it means moving from $post to $this->post_table

[adampatterson]

Removing $post = load::model('post') opens up more clear variables for controllers.

[adampatterson]

regular functions and static methods wont have access to the data_properties, this is needed for simplicity. Controllers and models have been adjusted.