refs #2433 Home-made getExtension() methods has been replaced by utility method provided by commons-io.

(cherry picked from commit 2b71e1f21f13da87208e78dedfebdd3a865f3237)

Conflicts:
	core-task-impl/pom.xml
	ding-impl/pom.xml
refs #2433 Null checks are replaced to empty string check since the new utility class returns empty string for file names without extension.

(cherry picked from commit 3b521eda6bea8cdbe6e58ee22833995ec7e80b50)