Show a dialog when the data folder is used by another openLCA instance

[msrocka]

The data folder (currently ~/openLCA-data-1.4) can only be used by one openLCA instance at the same time. If you start a second openLCA instance you get strange errors. Better would be a dialog which pops up when a second instance wants to use the same data folder. And even better would be a simple way to switch easily between different data folders (as it is done in Sophena for example).