restapi: RSDL - add 'deprecated' option

Mark parameter as deprecated in rsdl_metadata.yaml file this way:

example for signature parameter:
  vm.display.type--DEPRECATED: xs:string

example for url-param:
  max: {context: matrix, type: 'xs:int', value: 'max results', required: false, deprecated: true}

example for header param:
  Filter: {value: true|false, required: false, deprecated: true}

Change-Id: I5537c9065c13d9a68c88ab40ebf523bfe71e2a7b
Signed-off-by: Ori Liel <oliel@redhat.com>