IDL compiler: basic named property getters

Template a bit long b/c have enumerator and query as well.

Minor Perl CG changes to make order regular (callback after function),
and make code order match order of arguments in SetNamedPropertyHandler.

Some Python refactoring, since the contents of indexed and named operations
is the same: only the templates need to differ,
so we can share substantial code!

BUG=239771
R=haraken

Review URL: https://codereview.chromium.org/148813002

git-svn-id: svn://svn.chromium.org/blink/trunk@165989 bbb929c8-8fbe-4397-9dbb-9b2b20218538