Conflicts:
	src/test/java/org/orekit/errors/OrekitMessagesTest.java

These times scales may be used in SP3-c files.

The support is compliant with ISO-8601 standard.

Conflicts:
	src/main/resources/assets/org/orekit/localization/OrekitMessages_de.utf8
	src/main/resources/assets/org/orekit/localization/OrekitMessages_es.utf8
	src/main/resources/assets/org/orekit/localization/OrekitMessages_it.utf8
	src/main/resources/assets/org/orekit/localization/OrekitMessages_no.utf8
	src/main/resources/assets/org/orekit/localization/OrekitMessages_ro.utf8
	src/test/java/org/orekit/propagation/semianalytical/dsst/utilities/CoefficientFactoryTest.java

As users may need to propagate the estimated orbit, it is simpler for
users to directly get a fully configured propagator with the estimated
propagation parameters also set rather than get only the orbit. If only
the orbit is desired, it can be retrieved as the initial state of the
propagator.

Fixes issue #237