How to add the configuration changes from a website to another website?
There was a discussion in the Drush issue queue on allowing config-import to force the adoption of the UUIDs in the imported configuration to be inserted into the database.  The problem with allowing this is that this operation is equivalent to deleting all of your configuration (e.g. all of your content types) and then re-creating them, which has the side-effect of deleting all of the data associated with that configuration (e.g. all of the pages in your site).  It was thought that erasing a site entirely was too surprising of a side-effect for a config-import operation, even with a --force flag, so this use case will not be supported.

The current thinking is that the right time to force the UUIDs of a site to change would be at site-install time.  At the moment, the Drush site-install command does not support this directly; however, there is a configuration import installation profile that Alex Pott wrote that will perform this function.  It should be possible to use this from Drush site-install.

In general, though, if your use-case is moving configuration from one site to a different site, you should use features, not the configuration system.