Renamed configuration parameters.

## Configuration Parameter Renaming

This pull request updates all the configuration parameters across the command line, environment variables, and TOML config file. It also updates the underlying `Config` fields to match so it's not confusing across the codebase.


### Changes

Here's what's changed:

* `Name/-n`  → `Name/-name`
* `DataDir/-d`  → `DataDir/-data-dir`

* `AdvertisedUrl/-c` → `Addr/-addr`
* `ListenHost/-cl`  → `BindAddr/-bind-addr`
* `CAFile/-clientCAFile`  → `CAFile/-ca-file`
* `CertFile/-clientCertFile`  → `CertFile/-cert-file`
* `KeyFile/-clientKeyFile`  → `KeyFile/-key-file`

* `Peer.AdvertisedUrl/-s` → `Peer.Addr/-peer-addr`
* `Peer.ListenHost/-sl`  → `Peer.BindAddr/-peer-bind-addr`
* `Peer.CAFile/-serverCAFile`  → `Peer.CAFile/-peer-ca-file`
* `Peer.CertFile/-serverCertFile`  → `Peer.CertFile/-peer-cert-file`
* `Peer.KeyFile/-serverKeyFile`  → `Peer.KeyFile/-peer-key-file`

* `Machines/-C`  → `Peers/-peers`
* `MachinesFile/-CF`  → `PeersFile/-peers-file`

* `-f`  → `-force-config`
* `Cors/-cors`  → `CorsOrigins/-cors-origins`
* `WebURL/-w`  → `WebURL/-web-url`
* `SnapCount/-snapshot-count`  → `SnapCount/-snapshot-count`

Also, all the environment variables have been made consistent. Changes were as you would expect. One notable environment variable change was changing `ETCD_DATADIR` to `ETCD_DATA_DIR` for consistency.

Both the `README.md` and `external-documentation.md` have been updated to reflect the new changes as well as the functional tests.


### Related

Trello: https://trello.com/c/aTnnudQy/40-0-2-cleanup-all-of-the-flags

/cc: @philips @xiangli-cmu