What to do when "Spatial tables already exist" ?

I'm trying to re-install CKAN and reload the plugins but also re-use the same database as before.

As a result, I'm now getting this error and I'm not sure what to do about it.

```
[Fri Sep 09 03:48:43.703707 2016] [:error] [pid 24622:tid 140425162532608] 2016-09-09 03:48:43,703 DEBUG [ckanext.spatial.plugin] Setting up the spatial model
[Fri Sep 09 03:48:43.710203 2016] [:error] [pid 24622:tid 140425162532608] 2016-09-09 03:48:43,710 DEBUG [ckanext.spatial.model.package_extent] Spatial tables defined in memory
[Fri Sep 09 03:48:43.722223 2016] [:error] [pid 24622:tid 140425162532608] 2016-09-09 03:48:43,722 DEBUG [ckanext.spatial.model.package_extent] Spatial tables already exist
```

Start with the setup path in ckanext.spatial.plugin and the existing-table handling in ckanext.spatial.model.package_extent. Reproduce a CKAN re-install using the existing database, then determine the expected behavior when the spatial tables are already present and document or test that outcome.

Written by the indexing model from the issue text.