when generating complex types from an lxml element, inspect for xsi:type attribute so that appropriate subclass complex objects will be instantiated rather than base class objects

basically, attempt to honor polymorphism
changelog update
move async from flag to attribute
sqlalchemy: fix wrong assertion and make the safeguards in the case of array of primitives stored in sql table more consistent
minor
minor
add empty to_unicode to ProtocolBase
add to_unicode to ModelBase
use to_string functions that wouldn't produce anything outside ASCII as to_unicode handlers.
add file_to_unicode and implement text-only files
add to_unicode handlers for AnyXml, AnyHtml, Unicode, ByteArray and XmlAttribute
switch HtmlTable to to_unicode
changelog update
remove redundant paragraph
Merge pull request #385 from jrocnuck/master

generate correct complex type from lxml element
Merge remote-tracking branch 'arskom/master'
minor improvements to #385
changelog update
generalize xsi:type parsing #385
fix sqla regression due to "consistentization" :))