Businesslogic Integration: Extend powerGateServer Plugin with new version of ERP API

[PatrickGrub]

After the configurations new requirements for the ERP API were delivered, see #115 then:

• [ ] Include the new API into the plugin
• [ ] Extend metadata for the item and following functions:
  • [ ] Create
  • [ ] Update
  • [ ] Query
• [ ] Extend metadata for the BomHeader and following functions:
  • [ ] Create
  • [ ] Update
  • [ ] Query
• [ ] Extend metadata for the BomRow and following functions:
  • [ ] Create
  • [ ] Update
  • [ ] Query
  • [ ] Delete
• [ ] Extend metadata for the Documents and following functions:
  • [ ] Create
  • [ ] Update
  • [ ] Query
  • [ ] Upload
  • [ ] Download
• [ ] Extend the powershell test script with powerGate Commandlets