After excavating device info report save-path in a dialog.
Cleanup: Move nested functions to top of the enclosing function (part 1/2).

To keep changes small, indention levels are not corrected in this change.
Cleanup: Move nested functions to top of the enclosing function (part 2/2).

This change is only fixing the indention levels. Nothing else changed.
Use more spelling parameter name.
Remove unused parameter.
Cleanup: Evaluate pathname of download path only once.

It is now returned by the call to device_extract().
Minimalistic cleanup: Remove extraction dir just after .tgz is created.
Cleanup: Rename ugly variable and simplify bollena tests.
Let tarfile collect the files recursively instead of doing it ourselves.
Minor cleanup: Move some lines.
Remove unused resp. useless code.
Destroy extraction dialog instead of only hiding it.
Make print output more meaningful.