IBX-2355: Made inheritance of the naming methods possible

[konradoboza]

JIRA: https://issues.ibexa.co/browse/IBX-2355

In order to reuse methods pluralize and toCamelCase within https://github.com/ibexa/product-catalog/pull/456 we need to change their scope to be able to decorate the original implementation and avoid redundancy.

[adamwojs]

In order to reuse methods pluralize and toCamelCase within https://github.com/ibexa/product-catalog/pull/456 we need to change their scope to be able to decorate the original implementation and avoid redundancy.

IMHO it's worth to consider extracting interface from NameHelper but this could be done as follow up.

[konradoboza]

I reverted access modifiers, introduced an abstract class with common methods that can be accessed in other places, and went for decoupling pluralize method by moving it to a dedicated service. Please re-review @adamwojs @webhdx.