Merge pull request #54 from theponti/develop

Develop
Merge pull request #56 from theponti/develop

Develop
Merge pull request #58 from theponti/develop

Develop
Fix styles
Add owners to backpacks, folders, and items; Create category model
Add required:true for user reference on backpacks, folders, and items
Merge pull request #59 from theponti/user-associations

User associations