SelectItemGroup: escape and disabled properties are ignored

See: [https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=749](https://javaserverfaces.dev.java.net/issues/show_bug.cgi?id=749)

The implementation team has addressed the disabled handling, however, we can't
properly address the escape property for an attribute value without hacks to the
response writer (note: we've tried this in the past with mixed results).

Also See:
[https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=237](https://javaserverfaces-spec-public.dev.java.net/issues/show_bug.cgi?id=237)

As the fix for that will resolve this as well.
#### Environment
Operating System: All
Platform: All
#### Affected Versions
[1.2]

Start with the SelectItemGroup rendering path and read the linked implementation and specification issues, especially the discussion of disabled and escape handling. The work is done when both properties are honored without relying on response-writer hacks and the behavior matches the referenced specification fix.

Written by the indexing model from the issue text.