fixed freeze for install orphaned/yaourt package

when installing an AUR package (directly) via context menu from the
package list, the group tree would freeze and octopi wouldnt shut down
afterwards. this happened because octopi didnt find a suitable terminal,
but did wait for its execution.
This fix adds "konsole" as terminal for kde and will abort in case no
suitable terminal was found. also the info tab will not indicate
successfull completion in this case.