Add PTREE support for JSON and YAML names that have non-xml allowed characters

Try to use gpu with nvidia driver on Azure.

Azure VMSize: Standard_nc6s_v3

Required field in pod/job:

resources:
     limits:
       nvidia.com/gpu: 1

hpcc/values.yaml additional setting:

thor:

• name: thor
     prefix: thor
     numWorkers: 2
      maxJobs: 4
     maxGraphs: 2
     workerResources:
         nvidia.com/gpu: 1

Result yaml: 

thor:
   logging:
      detail: 80
   maxGraphs: 2
   maxJobs: 4
   name: thor
   numWorkers: 2
   prefix: thor
   vaults:
      ecl: null
      ecl-user: null
      storage: null
  workerResources:
      nvidia.com/gpu: 1

   .......

  image: hpccsystems/platform-gnn-gpu:8.2.4-az
  imagePullPolicy: IfNotPresent
  name: thorworker-HPCC_JOBNAME
  resources:
     limits:
       nvidia.com/gpu: 1

error :

kubectl logs thor-eclagent-79c66db78d-wzslt
00000000 USR ERR 2021-07-27 01:37:04.325 1 1 UNK "99: agentexec.cpp(398) : Error processing config file
: Error loading configuration file /etc/config/thor.yaml (invalid yaml): IPropertyTree: UNKNOWN ERROR CODE: -1
Invalid xml attribute: @nvidia.com/gpu"

Two students will try to test GNN with GPU on Azure. But it is optional