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}

example for entire signature:

      signatures:
      - mandatoryArguments: {}
        optionalArguments: {action.vm.os.initRd: 'xs:string', action.vm.domain.name: 'xs:string',
          action.vm.placement_policy.host.id|name: 'xs:string', action.vm.placement_policy.affinity: 'xs:string',
          action.async: 'xs:boolean', action.vm.os.kernel: 'xs:string', action.grace_period.expiry: 'xs:long',
          action.vm.display.type: 'xs:string', action.vm.stateless: 'xs:boolean', action.vm.os.cmdline: 'xs:string',
          action.vm.domain.user.username: 'xs:string', action.pause: 'xs:boolean',
          action.vm.os.boot--COLLECTION: {boot.dev: 'xs:string'}, action.vm.domain.user.password: 'xs:string'}
        deprecated: true

Change-Id: Ia7f4ccf1dfa29894f8791909f2284496e7d8b27c
Signed-off-by: Ori Liel <oliel@redhat.com>