Updates a single named field on an existing work order, identified by `workOrderId`, to the passed `value`. 
Call this when only one attribute needs to change � for example, bumping `workOrderStatusId` when a technician starts work, or reassigning `assignedTo` � 
without having to resend the entire work order dictionary as `updateWorkOrder` requires. 
`userId` is recorded for the audit trail (changedBy). 
Only the field names listed below are valid for the `field` argument.

---
### Parameters
**workOrderId** `Integer`: Id of workOrder to update<br />
**field** `String`: Valid options are title, description, assetId, procedureId, workOrderStatusId, workOrderPriorityId, maintenanceTypeId, scheduleTypeId, requestedBy, assignedTo, leadTimeDays, enabled<br />
**value** `String`: Value to update to<br />
**userId** `Integer`:Id of the user executing the function<br />

---
### Returns
**# of records modified** `Integer`<br />
**message** `String` None if success<br />

---
### Example
```python
# Mark a work order for HVAC-Unit-7 as "In Progress" once a technician starts the job
workOrderId = 6104
field = "workOrderStatusId"
value = 2
userId = system.kanoa.security.getIDPUserId({'userName': 'SYSTEM'})

recordsModified, message = system.kanoa.cmms.updateWorkOrderField(workOrderId, field, value, userId)
print recordsModified, message
```