qt: Undeprecate API that I find useful

* lang/qt/src/decryptjob.h,
lang/qt/src/decryptverifyjob.h,
lang/qt/src/signencryptjob.h,
lang/qt/src/verifydetachedjob.h,
lang/qt/src/verifyopaquejob.h: Undeprecate ByteArray based API.

While an IODevice may be more performant the ByteArray API is
a very easy way to get started with QGpgME as it allows you
basically to encrypt / decrypt any QString.

This also fixes a ton of deprecation warnings in KDE where this
API is used all over the place.