- Adding category table and category field in attribute table
- When getting types, sorting by category first, than by name

This is more flexible, since the file doesn't need to be in 'src/SGalinski/TypoScriptBackendBundle/Resources/Data/' directory

This makes properties of same type to be unique.
But, it doesn't make type names unique if the types extend different superType

WHERE attribute.deleted IS NULL OR attribute.deleted = FALSE

Exported file doesnt have versions because default versions (1.0 - 7.4) are removed from import function

- minVersion == NULL is treated as it is earliest version
- maxVersion == NULL is treated as latest (current) version

Also making some comments.

*In progress*

Returned attribute doesn't have sub objects (parent, type, children), instead it has parent_id and type_id.

- minVersion and maxVersion are of MySQL type NUMERIC(4,1) meaning that they support 4 digit versions with one digit behind decimal point e.g.: 6.2, 2.0, and not supported: 6.2.1, 4.21
- Adding minVersion and maxVersion attributes in type and property tags when exporting if minVersion/maxVersion fields are set in database records.
- Exporting by version - exports all types and properties which exist in passed version
- When importing, if minVersion/maxVersion is not set in property or type tag of tsref.xml, default values (specified by user) will be used

Also adding @return void statements where missing

Backend shouldn't depend of frontend

PUT (when modifies data) and PATCH methods are returning Content-type text/html, not application/json.
Not using json assertion on them.