fix(sql/drop): adjust drop constraint statements

related to CAM-2189
feat(caseExecutionQuery): query after disabled case executions

related to CAM-2192
feat(engine/scripttask): add ability to use external script resource

- script source can now be returned by an expression
- script source can now be loaded from an external script
- external scritps can be found in the deployment or the classpath
- the path for the external script can be returned by an expression

related to #CAM-2357