Extended GQL Parser: allow INSERT... SELECT... statements

```
Allow INSERT...SELECT... statements

INSERT INTO MyNewKind SELECT ... FROM MyOldKind WHERE ...

Keys with ids must be explicitly defined, otherwise new ids are generated:

INSERT INTO MyNewKind SELECT KEY('MyNewKind',KEY_ID(__key__)) as __key__ ...
```

Original issue reported on code.google.com by `vbarta...@gmail.com` on 16 Jun 2010 at 7:00
