Remove old metadata accessing method from
OdtDocument.
Add two more functions to DomUtils:

1. To map a flat map of strings onto a node,
thus creating a series of childnodes with
the key as the ns:localName, and the value
as the text content.

2. To do the reverse, generating a flat
string->string mapping from such elements.

For this, Namespaces.js get a function to
lookup the namespace prefix from the URI
 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.