Add support for pagination of list entries

[lincmba]

fixes #29

IMPORTANT: Where possible all PRs must be linked to a Github issue

Resolves [link to issue]

Engineer Checklist

• I have written Unit tests for any new feature(s) and edge cases for
  bug fixes
• I have run mvn spotless:check to check my code follows the project's
  style guide
• I have run mvn clean test jacoco:report to confirm the coverage report
  was generated at plugins/target/site/jacoco/index.html
• I ran mvn clean package right before creating this pull request.

[ndegwamartin]

@lincmba lets add some documentation on the READ ME

[ndegwamartin]

@lincmba see my comment here #29 (comment)

[ndegwamartin]

Tested out the implementation, the pagination itself works 👍🏾 but the pagination links are not returned.

Getting this as a response (tested with paginated count of 2):

{
    "resourceType": "Bundle",
    "id": "04bc098a-5ab8-42bb-ab5f-f9a2198f3900",
    "type": "batch-response",
    "link": [
        {
            "relation": "self",
            "url": "http://fhir-shared-stage-sync-hapi-fhir.opensrp.svc:8080/fhir"
        }
    ],
    "entry": [
        {
            "resource": {
                "resourceType": "Group",
                "id": "6f3980e0-d1d6-4a7a-a950-939f3ca7b301",
                ....

[ndegwamartin]

Additionally update the unit tests to verify that the (previous/next) pagination links are returned correctly (depending on provided _ count).

Note, the base url should be the same one from the request that was made.