add active delay to 'toxml' and 'to/from TML'

...a/tmltranslator/TMLActivityElementWithIntervalAction.java

src/main/java/tmltranslator/TMLDelay.java

src/main/java/tmltranslator/TMLTextSpecification.java

src/main/java/ui/ActivityDiagram2TMLTranslator.java

src/main/java/ui/tmlad/TMLADDelayInterval.java

.../test/resources/tmltranslator/expected/expected_spec1.tml

.../test/resources/tmltranslator/expected/expected_spec2.tml

.../test/resources/tmltranslator/expected/expected_spec3.tml

.../test/resources/tmltranslator/expected/expected_spec4.tml