handling for the given expression.
usage is like:  ${data | encoding('utf-8', errors='strict')}

further try/except AST fixes, cleanup of filter unit tests, made __locals propigation in codegen slightly simpler/faster

by the template but otherwise not affected

implemented "args" for <%page> tag.  still has a default
"**_extra_pageargs" catchall for now...

- more docs

more docs

occurs in a directory hierarchy resembling uri scheme

added filename-relative lookup to TemplateLookup

codepaths into the module (main render, inherit only, def call only)