Datatypes in observation object resources

[csarven]

Add appropriate datatypes to the object resources in observations when they are not explicitly given via structure:TextFormat in KeyFamily. This is really about checking literals for known patterns.

[csarven]

See also Issue #2

[csarven]

Commit fca8e69 detects xsd:decimal type and assigns rdf:datatype xsd:decimal . Otherwise left as literal.

Leaving this issue open for other enhancements.

[csarven]

For some of the Attributes e.g.:

<structure:Attribute isTimeFormat="true" assignmentStatus="Mandatory" attachmentLevel="Series" conceptAgency="ECB" conceptVersion="1.0" conceptRef="TIME_FORMAT">
    <structure:TextFormat maxLength="3" minLength="3" textType="String"/>
</structure:Attribute>

if a URI is not used, the literal shouldn't be datatyped. In the case above, the datatype is xsd:string and that's not fun to query with.