Configuration checks and hints

[wincak]

It is now possible to enter invalid configuration in the settings dialog because there seems to be no validity check. It would be more user friendly to show warning if for example you entered invalid character in the hostname or left some field empty. Also it would help users if they could see better what the different options are for. This could be done for example by adding appropriate placeholder text like "Server name" in "Name" field and "Server hostname or IP address" in the hostname field. And maybe some mouseover text for the other fields like the "Active" checkbox?