Create variable name pattern registry

[delgadom]

We're settling on a variable naming scheme for climate right now. What if we provided a way of registering archive name patterns, so that you only had to provide the list of tags and the pattern you'd like to use and the name was created for you?

Example usage:

$ datafs create --template=climate \
>   --project=GCP \
>   --team=climate \
>   --probability_method=SMME \
>   --variable=tasmax \
>   --geography=grid025  etc...

Probably depends on #295