Access method for getting the XGWRECORDID property from the calendar

Access method for getting the XGWRECORDID property from the calendar

* backends/groupwise/e-cal-backend-groupwise-utils.c:
( e_cal_component_get_gw_id): Access method for getting the
XGWRECORDID property from the calendar component.
( set_properties_from_cal_component): Range of priority value
HIGH extended to include values 1 and 2.
The X-EVOLUTION-GROUPWISE-ID is now referred as XGWRECORDID
for consistency with the ITIP messages.
( e_gw_item_to_cal_component) : Absence of due_date does not
invalidate the task component. Fixes #60926.
( e_gw_connection_send_appointment),( e_gw_connection_create_appointment):
Implemented.
( e_gw_connection_get_freebusy_info):
( e_gw_item_set_changes): Fixed compiler warnings.

* backends/groupwise/e-cal-backend-groupwise-utils.h:
Declarations for added functions.
* backends/groupwise/e-cal-backend-groupwise.c:
( populate_cache) : Removed unused variables.
( set_container_id): Extracted a function out of the code as it is
used twice.
( e_cal_backend_groupwise_create_object): Handle changes in the SOAP interface.
The server now returns CVSa list of uids. This is to allow creation of recurring
calendar events.
( e_cal_backend_groupwise_modify_object): Fix some leaks.
( e_cal_backend_groupwise_remove_object), ( receive_object),
( send_object), ( e_cal_backend_groupwise_send_objects): Use the newly created
functions for handling group calendar items.
* e-gw-connection.c:
( e_gw_connection_new) : Fix for #59471 by getting around the server
defect. Substitute the first . by @.
( e_gw_connection_get_deltas): Fix for #56853. The server may indicate
that there are changes but not provide deltas if they are outside our
interest. This is now considered a valid response.
( e_gw_connection_send_item): Handle the change in the SOAP interface.
The sendItemResponse now returns a list of ids.
( e_gw_connection_accept_request), ( e_gw_connection_decline_request),
( e_gw_connection_retract_request), ( e_gw_connection_complete_request):
Implemented.
+
* e-gw-connection.h: Declaration for the added functions.
+
* e-gw-item.c:
( e_gw_item_new_from_soap_parameter): Add organizer only if the item
source is not 'personal'. Use 'priority' instead of Taskpriority for
Todos as recommended by the server team.
( e_gw_item_set_calendar_item_elements): Organize common properties
to Appointments and todo-s into a separate function.
( e_gw_item_append_to_soap_message),
( append_event_changes_to_soap_message),
( e_gw_item_append_changes_to_soap_message): reorder soap elements
in the sequence specified by the schema. The server does not enforce this
but doing it right anyway..