Implementation of Time datavalue.
Minor style changes
Implementation of globe coordinates value
Return only unmodifiable collections
Direclty use member fields in equal()
Initial implementations of EntityRecords
+license texts
Introduce factory for creating data objects

The constructors of all data object implementations are
package private now, so users can only create them with
the factory. The factory can implement canonization and
other magic later on if needed.
Fix spelling error
Merge pull request #1 from Wikidata/datamodel-basic-implementation

Further implementation of data model