Added support for SPIN attitude mode in ADM files.

src/main/java/org/orekit/errors/OrekitMessages.java

...ain/java/org/orekit/files/ccsds/ndm/adm/AttitudeType.java

...in/java/org/orekit/files/ccsds/ndm/adm/aem/AemParser.java

...in/java/org/orekit/files/ccsds/ndm/adm/aem/AemWriter.java

...ava/org/orekit/files/ccsds/ndm/adm/aem/AttitudeEntry.java

...main/java/org/orekit/files/ccsds/ndm/adm/apm/ApmFile.java

...ces/assets/org/orekit/localization/OrekitMessages_da.utf8

...ces/assets/org/orekit/localization/OrekitMessages_de.utf8

...ces/assets/org/orekit/localization/OrekitMessages_el.utf8

...ces/assets/org/orekit/localization/OrekitMessages_en.utf8

...ces/assets/org/orekit/localization/OrekitMessages_es.utf8

...ces/assets/org/orekit/localization/OrekitMessages_fr.utf8

...ces/assets/org/orekit/localization/OrekitMessages_gl.utf8

...ces/assets/org/orekit/localization/OrekitMessages_it.utf8

...ces/assets/org/orekit/localization/OrekitMessages_no.utf8

...ces/assets/org/orekit/localization/OrekitMessages_ro.utf8

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

...g/orekit/files/ccsds/ndm/adm/aem/AEMAttitudeTypeTest.java

...ava/org/orekit/files/ccsds/ndm/adm/aem/AEMParserTest.java

...ava/org/orekit/files/ccsds/ndm/adm/aem/AemWriterTest.java