fix(oracle simulator): proper response on get participants with partySubIdOrType

[shashi165]

Summary

1. Made the structure of the result of request GET oracle/participants/{Type}/{ID}?partySubIdOrType={SubId} to be consistent with the result of GET oracle/participants/{Type}/{ID}
   i.e.

{ 
  partyList: [ { fspId: 'testfsp2', currency: 'XOF', partySubIdOrType: undefined } ] 
} 

AND

{ 
   partyList: [ 
     { fspId: 'testfsp1', currency: 'XOF', partySubIdOrType: '10' }, 
     { fspId: 'testfsp1', currency: 'XOF', partySubIdOrType: '20' }, 
     { fspId: 'testfsp1', currency: 'XOF', partySubIdOrType: '30' }, 
     { fspId: 'testfsp1', currency: 'XOF', partySubIdOrType: '40' } 
   ] 
 } 

2. Modified POST oracle/participants/{Type}/{ID} to allow multiple records to be created based on different partySubIdOrType. Earlier it was allowing to create only 1 record per {Type} and {ID} ignoring partySubIdOrType

[vgenev]

👍