Experiment creator state flags

[arik-shurygin]

the create_experiment script will now delete the states/ directory of the experiment by default, meaning that multiple calls to create_experiment will not append more states in the states/ directory, all files will be removed and then your new selection will be placed within.

The reason this change was made was due to bugs that would arise when a user made multiple calls to create_experiment with different states passed through the -s flag where stale states were not being removed and would be launched along with the intended states.

Furthermore this PR adds two new flag options with the -s:
all still creates a directory for every state/region/territory (including all HHS regions, Puerto Rico, and DC)
hhsregions creates 10 directories, one per region
50states creates one directory per state (excluding DC/PR/US).

Also pushed some code used to generate a single combination CSV so the create_experiment script does not need to load/parse separate files anymore.
CLOSES #3

[kokbent]

let's go!