OPENDJ-1308 Migrate schema support

Moved a lot of duplicate code to static methods in CommonSchemaElements.
Removed many methods from server types that do not exist on the SDK types.


AttributeType.java, DITContentRule.java, DITStructureRule.java, LDAPSyntaxDescription.java, MatchingRuleUse.java, NameForm.java, ObjectClass.java:
Moved recreateFromDefinition() to Schema.
Moved getDefinitionWithFileName() to CommonSchemaElements.
Removed getSchemaFile(), setSchemaFile() and setExtraProperty(), replaced by the eponymous static method in CommonSchemaElements.
Removed 

SchemaFileElement.java:
Added getExtraProperties().
Removed getSchemaFile(), setSchemaFile() and recreateFromDefinition().

CommonSchemaElements.java:
Now implements SchemaFileElement.
Removed getExtraPropertyNames(), getExtraProperty().
Added getExtraProperties()
Made getSchemaFile(), setSchemaFile() and setExtraProperty() static.
Extracted static method getSingleValueProperty().

Schema.java:
Moved all recreateFromDefinition() methods here.

*.java:
Consequence of all these changes.