Minor changes/additions on the tests

- removed (commented) test #0286 (@value is no longer considered for HTML5+RDFa)
- 'moved' the property copy tests (321-327) to the 'main' branch of testing (property copy is a required feature).
- changed 0278 which gave a higher priority to @datetime over @content (and that has changed)
- added a test on @content overwriting the content of the <time> element

Ivan

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Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
FOAF: http://www.ivan-herman.net/foaf.rdf