Support Multiple Config Repos

[Miro-H]

Add support for multiple config repos to the Ansible master. This includes commands to maintain a list of repositories and short names for them, and an argument to specify the short name whenever the benchmark is run. The Ansible master should then switch to the respective repository and execute the experiments there.

Think about how we could simplify this setup. E.g., we could bind channels to repos:

Channel A -> repo1
Channel B -> repo2

and then always execute configs from repo1 if the command was sent from Channel A (so that the user does not always need to specify the repo).