Optionally don't overwrite config when installing xswiftbus

[oktal3700]

Users get frustrated when installing a new version of xswiftbus causes the xswiftbus.conf to be overwritten with default values. There should be a checkbox in the installation dialog so they can choose whether or not to overwrite it.

[oktal3700]

Suggestion by @emiro85: instead of the above, store the user's config in a new file xswiftbus.conf.local. The new file is not overwritten when installing xswiftbus. The old file xswiftbus.conf is used for default values but the new file takes priority and can override the defaults.