Add ability to fetch Tendermint config/data from nodes

Sometimes we'd want to be able to grab all of the configuration/data from the Tendermint nodes we're testing. We should have a `tmtestnet network fetch_tmhome` command that will go to all desired Tendermint nodes and fetch their Tendermint home directories (this will be in `/home/tendermint/.tendermint`), bringing all of their configuration/data back to the local machine.

```bash
# Fetch all Tendermint node groups' config/data
./tmtestnet.py network fetch_tmhome /save/me/here

# Fetch specific node and node groups' config/data
./tmtestnet.py network fetch_tmhome /save/me/here my_validators "my_seeds[0]"
```

For this we'll most likely need an additional [Ansible script](https://github.com/interchainio/testnets/tree/master/tendermint/ansible) (perhaps `fetch-tmhome.yaml`).