fixed bug where stepProperties were not cleared before saving

Conflicts:

	plugins/frontlinesms-core/grails-app/domain/frontlinesms2/WebconnectionActionStep.groovy
	plugins/frontlinesms-core/grails-app/services/frontlinesms2/CustomActivityService.groovy
Merge branch 'CORE-1703' of github.com:frontlinesms/frontlinesms2 into CORE-1703