Remaining tasks from GPU release (0.5)

[daurer]

Todo for future release:

• (Unify logging messages: log(level, message) vs. logger.info, logger.warning, etc.)
• Make all engines compatible with live processing (Remove traces of OpenCL engine #311) -> next release
• (clean up branches/issues)
• revisit tests, move to unity-tests, use relevant array sizes. Archive cuda-ext tests. improve unit tests by introducing more unity tests and larger array sizes. archive unused tests #345
• archive unused ("testing") kernels Archive unused "testing" kernels #343
• (automated tests for the gpu part. maybe at NERSC? DLS?)
• (Check all parameters for userlevel flag and implement accordingly)
• (merge upsampling PR (WIP: Upsampling/Downsampling kernels #305))

[bjoernenders]

All the above comments have been migrated to their own issues with the appropriate labels. closing this.