v0.9.2

Minor fix release.

• Additional fix to handling lowercase reference sequences.
• Fix bug in creation of RLE alignments.
• Update update_model.py script.
• Remove option to select labelling scheme during training.
• Unify how LabelSchemes store training data.

Please do not attempt to use the "Source code" assets attached below for running medaka, they do not include medaka's model files.