Services/NAT: Added basic functionality.
Revisited `package.json`.
Global revision.
Changed config system to use environment vars and `nconf`.
* Added basic test coverage support.
* Added tests for `system/info` path.
`system/settings`:
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.
`system/tunables`:
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.
* Added POST action to the collection.
`system/logging/logs`:
* Added tests.
* Updated error messages with new form.
* Added DELETE action to the resources.
`system/logging/settings`:
* Added tests.
* Updated error messages with new form.
* Added PUT action to the resources.

Global:
* Changed all references to `logger` to be global ones to being able to change its settings dynamically.
`system/logging/settings`: Removed TODO.
TODO file: Removed task already done.
`interfaces/ethernets`:
* Stripped included addresses.
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.

`interfaces/addresses`:
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.
`interfaces/loopbacks`:
* Stripped included addresses.
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.
`interfaces/vlans`:
* Stripped included addresses.
* Added tests.
* Changed PATCH for PUT.
* Updated error messages with new form.