Service Group feature

[mamullen13316]

Added ability to get/create/update Service Groups.

• get_service_group()
• create_service_group()
• update_service_group()

Also made description an optional argument across all methods.

>>> fw.create_service(name="test_svc1", service_type="TCPorUDP", service_list=[{"dst_port": "1111", "protocol": "tcp"}])
Out[5]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'Services': {'@transactionid': '',
   'Status': {'@code': '200',
    '#text': 'Configuration applied successfully.'}}}}

>>> fw.create_service(name="test_svc2", service_type="TCPorUDP", service_list=[{"dst_port": "2222", "protocol": "tcp"}])
Out[6]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'Services': {'@transactionid': '',
   'Status': {'@code': '200',
    '#text': 'Configuration applied successfully.'}}}}

>>> fw.create_service_group(name="test_sg1", service_list=["test_svc1"])
Out[7]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'ServiceGroup': {'@transactionid': '',
   'Status': {'@code': '200',
    '#text': 'Configuration applied successfully.'}}}}

>>> fw.get_service_group(name="test_sg1")
Out[8]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'ServiceGroup': {'@transactionid': '',
   'Name': 'test_sg1',
   'Description': None,
   'ServiceList': {'Service': 'test_svc1'}}}}

>>> fw.update_service_group(name="test_sg1", service_list=["test_svc2"])
Out[9]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'ServiceGroup': {'@transactionid': '',
   'Status': {'@code': '200',
    '#text': 'Configuration applied successfully.'}}}}

>>> fw.get_service_group(name="test_sg1")
Out[10]: 
{'Response': {'@APIVersion': '2000.2',
  '@IPS_CAT_VER': '1',
  '@IS_WIFI6': '0',
  'Login': {'status': 'Authentication Successful'},
  'ServiceGroup': {'@transactionid': '',
   'Name': 'test_sg1',
   'Description': None,
   'ServiceList': {'Service': ['test_svc1', 'test_svc2']}}}}