Consider changing kiwi PagingParams to use our own KiwiSort.Direction instead of Spring Data's Sort

[sleberknight]

The kiwi PagingParams currently uses Spring Data's Sort.Direction but really should not use it.

In addition, this entire paging infrastructure could be moved outside the org.kiwiproject.spring.data package and into a more generic one, e.g. org.kiwiproject.search.paging or similar.

At first glance, the classes in org.kiwiproject.spring.data that are generic in nature (or could be made generic) include:

Class/Interface	Status
KiwiPage	generic
KiwiSort	generic
KiwiSort.Direction	generic
PagingParams	can make generic
PagingRequest	can make generic

The rest of the classes in org.kiwiproject.spring.data (as of this writing) are directly dependent on Spring Data APIs, so this would entail splitting the existing package such that the org.kiwiproject.spring.data package depends on the new, generic package.

This would obviously be a breaking change to a public API and so should be done by first deprecating the existing classes, and then releasing the changes in a new major version of kiwi.

[sleberknight]

Actually a better way to go about this at present is to replace (some) classes in kiwi's spring.data package with generic versions that have no dependence on Spring, e.g. KiwiPage and KiwiSort do not have dependence on Spring but reside in the spring.data package.

PagingParams and PagingRequest both depend on Spring Data's Sort, but this dependency can easily be broken and changed to use KiwiSort for example. These could be moved along with KiwiPage and KiwiSort to the generic package.

If necessary, we can also create adapter methods to translate between KiwiSort and Spring Data's Sort. These adapters should live in the kiwi spring.data package.

Essentially, these and possibly other classes would be copied to a new generic package, and deprecate the existing ones, possibly for removal in a future version.