Add more features to the global settings dialog

[diederik]

The global settings dialog is not finished yet.

Some ideas to improve it:

• Port range for file transfer (default 6891 - 6900). This is a requested feature.
• Whether the firewall will prevent any incoming connection (see ticket #179)
• Whether UPnP may be used to open ports (default: yes)
• Whether to force using the HTTP connect method.
• Webcam settings
• Large cards to display the accounts in the Accounts Manager, instead of ListViewItems.

Suggestions for labelling:

• "Allow KMess to configure my Internet connection device for fast file transfers (uses UPnP, {learn more})"
• "Port for UPnP broadcast responses: [default 1900]"

[diederik]

Added note about firewall, also see ticket #179