simpledb nexttoken fix

* patched php_sdb2's listDomains() function to save NextToken so we can actually get to all our was sdb domains
* updated GO_Simple_DB::check_domains() function to page through all the aws sdb domains we have.

related to https://github.com/GigaOM/legacy-pro/issues/1111, https://github.com/GigaOM/gigaom/pull/4282, and https://github.com/GigaOM/gigaom-plugins/pull/1841

i've also submitted [the patch to php_sdb2](https://github.com/g-g/php-sdb2/pull/2) to its author. hopefully it'll be accepted soon.