* [WiP] improve load_examples
related to #7472, longer term we will generate the examples by exporting
them into tarball as in #7472. In the meantime, we need this subset of
the features:
* allowing specifying an alternate database connection for examples
* allowing a --only-metadata flag to `load_examples` to load only
dashboard and chart definitions, no actual data is loaded
* Improve logging
* Rename data->examples
* Load only if not exist
* By default do not load, add a force flag
* fix build
* set published to true
