Added configuration module for ssh client.
Sets some basic settings and sets a general structure for the ssh
folder:
```
.ssh/
|- config
|- conf/
|---|- config.ssh
|----- hosts.ssh
|- keys/
|---|- id_*
------ id_*.pub
```
Config only refers to the files situated in `conf/` directory, while any
`hosts.ssh` configuration redirects to the correct keyfiles lying in
`keys/`.
Actual settings can be configured in `config.ssh` and this file is also
committed to versioning, whereas keys and hosts are not.
