Added customizable checks for units in parsing.

src/design/ccsds-lexical-analysis-sequence-diagram.puml

src/design/ccsds-parsing-class-diagram.puml

.../java/org/orekit/files/ccsds/ndm/ParsedUnitsBehavior.java

src/main/java/org/orekit/files/ccsds/ndm/ParserBuilder.java

src/main/java/org/orekit/files/ccsds/ndm/adm/AdmParser.java

...g/orekit/files/ccsds/ndm/adm/RotationXmlTokenBuilder.java

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

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

.../org/orekit/files/ccsds/ndm/adm/aem/AttitudeEntryKey.java

...in/java/org/orekit/files/ccsds/ndm/adm/apm/ApmParser.java

.../org/orekit/files/ccsds/ndm/adm/apm/ApmQuaternionKey.java

...in/java/org/orekit/files/ccsds/ndm/adm/apm/ApmWriter.java

src/main/java/org/orekit/files/ccsds/ndm/adm/apm/Euler.java

...ain/java/org/orekit/files/ccsds/ndm/adm/apm/EulerKey.java

.../java/org/orekit/files/ccsds/ndm/adm/apm/ManeuverKey.java

...ekit/files/ccsds/ndm/adm/apm/SpacecraftParametersKey.java

...org/orekit/files/ccsds/ndm/adm/apm/SpinStabilizedKey.java

...rg/orekit/files/ccsds/ndm/odm/CartesianCovarianceKey.java

.../org/orekit/files/ccsds/ndm/odm/KeplerianElementsKey.java

src/main/java/org/orekit/files/ccsds/ndm/odm/OdmParser.java