set version to 0.2.0beta3
support copying to mtp devices on KDE

Implemented using KDE's kio architecture.

refs #2120
abort transfer if savedir is invalid

"valid" here doesn't necessarily equal a real dir in the FS, as
in the case of KDE it's a kioslave path (mtp:/)

refs #2120
write qrcode to disk to workaround outdated packages

manually reverts 91c2b11b903903a0cd71a047bb361c7448c40c4c

refs #2124