[views] extend HTMLStream API to be able to change doctype / xmldecl
When generating RDFa (for instance), the doctype must be :
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN"
"http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd">
This changeset adds a ``set_doctype()`` method on request objects to allow
such changes during page generation.
add_attribute('TrInfo', 'tr_count')
sync_schema_props_perms('TrInfo')