Make FiltaQuilla UI more accessible, explain that actions and search terms are integrated in Thunderbird Filter editor

[RealRaven2000]

There is a criticism that user cannot find the user interface of the additional functions of FiltaQuilla, without opening the built in Filter editor. Apart from the settings in Add-ons Manager, FiltaQuilla does not have a dedicated user interface, it just modifies the Thunderbird UI with additional options.

There currently is only a short sentence on top of FQ settings - this can be easily overlooked.

• One suggestion would be to add a toolbar button (browser action in Tb115) that can be used to open the settings.
• A quick help dialog message that explains the fact above better would also be helpful