Add a new odf.MetadataManager to lib/odf.

 This handles setting and getting of various metadata
 fields, by providing methods setMetadata and getMetadata
 which take and return flat mappings between strings.

 This has been limited to work with only a few
 blessed metadata fields for now.

 ops.OpUpdateMetadata can be issued by either the server
 or a client once a gui for editing things like title
 is implemented.
Handle signalOperationExecuted in OdtDocument
and if it is an operation that was an 'edit',
handle the updating of dc:creator, dc:date,
and meta:editing-cycles.
* Add webodfversion.js.in (thanks Friedrich!)
to track the webodf version in js.
* OdfContainer gets updateMetadataForSaving,
which is called just before saving
and updates dc:generator.
Added OT for UpdateMetadata.

Add capabilities to OperationTests.js
and to TransformationTests.js,
test for <office:meta> elements.

Add corresponding tests for
OpUpdateMetadata.