adding report_on_update_only option to reporting

Author: Naor Livne

docs/config/worker.md

@@ -21,6 +21,7 @@ The following table shows the config variables used to set nebula worker at star
 | nebula_manager_check_in_time       | NEBULA_MANAGER_CHECK_IN_TIME     | 30                           | 30                                                                                                                   | int    | the time (in seconds) the device will check in with the Nebula manager to see if any changes to the application happens, the lower this is the faster changes to any app or device_group will propagate to the device but the higher the load to the manager will be so more mangers will be needed                                                    | yes      |
 | device_group                       | DEVICE_GROUP                     |                              | smart_fridge_device_group                                                                                            | string | the device group to attach a device to - each device can only exist in a single device_group but each device_group can have unlimited apps in it                                                                                                                                                                                                       | yes      |
 | reporting_fail_hard                | REPORTING_FAIL_HARD              | true                         | false                                                                                                                | bool   | part of the optional reporting system, if true any failures in the reporting system will fail hard and restart the worker and if false will attempt to continue, setting to false will mean that a lot of errors will need to be manually fixed by the admin                                                                                           | no       |
+| report_on_update_only              | REPORT_ON_UPDATE_ONLY            | false                        | true                                                                                                                 | bool   | part of the optional reporting system, if false(the default) will send all reports to kafka and if true will only send reports which have had a change in the device configuration in them.                                                                                                                                                            | no       |
 | kafka_bootstrap_servers            | KAFKA_BOOTSTRAP_SERVERS          |                              | mykafka.mydomain.com:9092 or empty                                                                                   | string | part of the optional reporting system, the FQDN\ip address of the bootstrap kafka nodes, if not set everything regarding the optional reporting system will be unused, setting it to any value is the trigger to turn on the reporting component of the workers                                                                                        | no       |
 | kafka_security_protocol            | KAFKA_SECURITY_PROTOCOL          | PLAINTEXT                    | PLAINTEXT, SSL, SASL_PLAINTEXT, SASL_SSL                                                                             | string | part of the optional reporting system, Protocol used to communicate with the kafka brokers, valid values are PLAINTEXT, SSL, SASL_PLAINTEXT or  SASL_SSL                                                                                                                                                                                               | no       |
 | kafka_sasl_mechanism               | KAFKA_SASL_MECHANISM             |                              | PLAIN or empty                                                                                                       | string | part of the optional reporting system, string picking sasl mechanism when security_protocol is SASL_PLAINTEXT or SASL_SSL. valid values are PLAIN or EMPTY, leaving empty\undefeind will mean sasl is not used                                                                                                                                         | no       |