Check compiled code against java6 api signature

Usage of the animal-sniffer-maven-plugin now avoids introducing code that
depends on a newly java7 (or later) api
Enforce dependencies do not require java 7+

This done with the maven enforcer plugin with the enforceBytecodeVersion
codehaus extra rules
Format to use spaces instead of tabs
Remove unused code
Add http delete with body
Return entity from DELETE method
add test scenarios
Merge pull request #87 from redfish4ktc/ensure-working-java6-build

Ensure working java6 build
SOAP-2280 Select JSONPath in Get Data menu
SOAP-2280 Select JSONPath using button in Property transfer desktop panel
SOAP-2280 JsonPathFacade class encapsulating library, including write support + moved JSON related methods
SOAP-2280 JsonPath write support in GUI + refactoring
Workaround for circular dependency problem
SOAP-2280 Transfer JSON number or node "as is" and not as string
SOAP-2280 Select JSONPath in Get Data menu
SOAP-2280 Selection of transfer language in Property transfers panel
SOAP-2280 Ensured the correct path language is set when creating a property transfer + removed duplications
SOAP-2280 Select JSONPath in Get Data menu
SOAP-2280 Select JSONPath in Get Data menu
SOAP-2280 JsonPathFacade class encapsulating library, including write support + moved JSON related methods