Update CHANGELOG

CHANGELOG

+5.4.3
+* Include possibility to set timestamp from external source on relevant records
+* Include the possibiliy of start systems with 1 board in secondary mode
+* Remove unused files (included register templates )
+* Improve tests
+
 5.4.2
 * Fix bug when the output calibration table has 2 different egu values for the same raw value
 https://jira.esss.lu.se/browse/ICSHWI-7619