How to delete all subresources in webservices.rest

@darius, new pull request: https://github.com/openmrs/openmrs-module-webservices.rest/pull/185

MainSubResourceController.java is a major change, having difficulty with git, but changes are at the end of the file, from line 168 onwards.

some changes are some problem to do with the git pull: ConversionUtil,java, ConversionUtilTest.java & SwaggerSpecificationController.java. I did not change these files.

some changes are going into openmrs-core to support this pull request including adding UUID support to allergy.