This commit removes usage of Categories queries in order to support
postgres. The Categories in postgres is an enum instead of a table and
we don't need to use the table in sqlite because the value are hardcoded
in the html and are unlikely to ever change.
This commit breaks the thumbnails in the index. Other functionality
needs to be tested before merging.
Configurations are separated in files in the folder config
Connection to database by a package to import when needed
Models will be in a model package for better maintenance
Services access to the models
Utils are tools or functions that can be used anywhere
main.go cleaned a bit and other files modifications are there for the above modifications
