Support Slice in the PagedResourcesAssembler

[anthony-foulfoin]

Hi,

Sometimes we cannot have informations such as the total elements and total pages of a request, that's where we're using a Slice instead of a Page.
But the PagedResourcesAssembler does not allows to convert a Slice to a Resource, it would be great to add a toResource(Slice<T> entity) method, or even add SlicedResourcesAssembler class.

[odrotbohm]

That needs to go into Spring Data Commons actually as this is where PagedResourcesAssembler lives. I've created DATACMNS-845 for that.