TileDB-SOMA 0.5.0a6

New features added

• [python] Enable Unicode non-indexed columns by @bkmartinjr in #777

Minor changes

• [r/python] Rename sidf to sdf [trivial] by @johnkerl in #776
• [python] Change _CachedElement._TdbInfo.type from str to type by @gsakkis in #775
• [python] A bit more deadstrip by @johnkerl in #781
• [python] Enhance value filter unit tests by @bkmartinjr in #785
• [python] Additional experiment-query unit tests by @bkmartinjr in #789
• [python] refactor SOMAReader construction into TileDBArray base helper method by @mlin in #787
• Simplify to_tiledb_supported_array_type by @gsakkis in #790

Bug fixes

• [python] Undo AWS_DEFAULT_REGION workaround by @johnkerl in #771