Create request interceptor class to remove namespace attribute from xml request bodies

Create request interceptor class to remove namespace attribute from xml request bodies

- add interceptor that removes xmlns attribute from xml bodies
- update eclipse persistence (2.6.2 -> 2.7.7)
- use spring-boot-starter-test instead of spring framework's spring-test
- bump snapshot version to 1.14.7-SNAPSHOT
- remove unused imports

Issue-ID: AAI-3976
Change-Id: Iac7103ae003cb7bb7269ada983af97e003be155c
Signed-off-by: Fiete Ostkamp <Fiete.Ostkamp@telekom.de>