This will give us the ability to specify different config options for
different dataroots.
the key of the dataroot dictionary is no longer the same as the dataroot_url.
Previously key==dataroot_url, and now those are separated.
Added an "is_multi_dataset" function to simplify logic where it branched on single vs multi.
Simplified the rest.py interface by no longer passing in the user annotations object, since
that can be retrieved from the dataset.
* app_config, fix bug with list/tuple command line arguments.
There was a error caused by pyyaml using lists, and click using tuples.
Now tuples are automatically converted to lists when the config is
updated.
fixes an issue with "cellxgene launch" which had a bad interaction between
command line parameters and config file parameters.
Now, the config files are applied first, followed by the parameters that
were provided in the command line.
There is also now a check that each of the config attributes is type checked.
