Move Vcloud::QueryRunner under Vcloud::Core

Move `Vcloud::QueryRunner` to the `Vcloud::Core::QueryRunner` namespace
so as to avoid conflicts with other Gems such as
['vcloud'](http://rubygems.org/gems/vcloud).
Remove extraneous line at end of file
Update CHANGELOG to reflect breaking changes

Update CHANGELOG to reflect breaking changes to Vcloud::Query and
Vcloud::QueryRunner.