module to set hostname and domain

[rekup]

Is your feature request related to a problem? Please describe.
This is a feature request to create the first module which should be able to set the hostname and domain (System -> Settings -> General

Describe the solution you'd like
The module should be able to configure the hostname and the domain of an opnsense instance. The naming will be as defined in #13 (comment)

[DonGiovanni83]

Since we have those features since #21 inside the system_settings_general module, I am going to close this issue.