Configuration: handle hostnames in booth.conf file

[ChrisKowalczyk]

Currently, booth fails to handle hostnames provided in booth.conf file. The changes proposed in this ticket will allow users to specify the sites as hostnames, instead of having to use IP addresses.
After resolving the hostname, the handling of the received IP address is the same as before.

[dmuhamedagic]

This introduces another layer (DNS) which may fail. Is it worth it? Further, please follow the coding style already there, i.e. braces following if expressions and comments.

[ChrisKowalczyk]

Well, I agree, it introduces a new layer that may fail, perhaps like most new functionalities. However, using hostnames, for example by defining them in hosts file, could be beneficial for users, especially that they would have to use a hostname specifically in the Booth config file. For those preferring to use IPs nothing will change. Also, I think that similar approach is used in other HA applications (corosync?).

[dmuhamedagic]

OK. Thanks for the contribution!