save last chosen setting and file in the "Add DTM window" and multiple DTM adding

[hansheiri]

When adding multiple DTMs to a project it would be very helpful if the last chosen setting and file would still be selected. Right now, for every new DTM I need to choose the correct protocol and refind my device type in a huge list of files.

Also it were helpful to being able to add multiple DTMs from the same type at once.