XML content support on get a node

XML content support on get a node

Here to bring Support for XML Response Entity In GET A NODE

- Made changes in components.yml to support contentType as
   application/xml
- Add ContentTypeInheadr in cpsDataV2.yml to support application/xml
- Add contentTypeInHeader parameter to accept xml  in
    DataRestController.java
- Implemented Logic to convert DataMaps To XML Data
- written testcase for above changes made

Issue-ID: CPS-2280
Change-Id: Ibe7ffb66ccbb03703626132c6d5c2eade0e7ab4b
Signed-off-by: Rudrangi Anupriya <ra00745022@techmahindra.com>