Final packaging refactoring

The current hcm (Maven) module artifact naming and (Java) packaging will be refactored to be more in alignment with common conventions and functional expectations:

• rename engine module to model module
• rename backend module to repository module
• add new migration module
• move api module package o.o.cm.api.model.action to o.o.cm.model
• move api module package o.o.cm.api.model to o.o.cm.model
• move api module package o.o.cm.api to o.o.cm
• move model module package o.o.cm.impl.model to o.o.cm.model.impl
• move model module package o.o.cm.impl.model.builder to o.o.cm.model.builder
• move model module package o.o.cm.engine.mapper to o.o.cm.model.mapper
• move model module package o.o.cm.engine.parser to o.o.cm.model.parser
• move model module package o.o.cm.engine.serializer to o.o.cm.model.serializer
• move model module package o.o.cm.engine to o.o.cm.model
• move model module package o.o.cms7.autoexport to o.o.cm.engine.autoexport in repository module
• move model module package o.o.cm.migration to migration module
• move repository module package o.o.cm.backend to o.o.cm.engine