XD-1807 Paging support for repositories

- Add utility class `PagingUtility` that returns the page implementation of
the given `Comparable` list
  - Make `ModuleMetadata`, `ContainerAttributes` and `ModuleDefinition` of type
`Comparable`
  - Update all the repositories `findAll(Pageable)` to use type specific
PageUtility's paged data
- Fix tests
I believe the null check here isn't needed because the REST controller would always provide **non-null** `Pageable` implementation from PageableHandlerMethodArgumentResolver. On the defensive side, may be we can add an assertion at PagingUtility.