API: FIX removed &amp; entities within CDATA (view.tpl.xml)

This is unnecessary, we already have CDATA.
API: FIX ensure empty xsdmf_value tag for items that have multiple values but nothing set.
API: TIDYUP Improve error messages, tidy up some markup.
API: FIX edit metadata now presents dates in format that can be re-submitted.

Also
* handle empty dates (class.api)
* attempt to make the date handling logic (year vs ymd) a bit clearer (class.api)
* improve date parse error messages
API: FIX handle internal author links (author_suggestor / attached xsdmf id's).
API: FIX Administrators should get cv_selector rooted in $parent_id.
API: FIX Controlled vocab items displayed properly in xml when editing record.
Merge pull request #19 from danielbush/master-api-date-multiple-values

Master api date multiple values