add support for units to DataTag
disallow "" as valid unit, must be given as "none"
moved docstring of unit sanitizer to util header
none unit testing, fixes
improve getOffsetAndCount to handle optional extents and units
add test case for valid and invalid units in DataTag
enable unit sanitizer during setting of units, added test
unit setter improved using transform and lambda construct
Merge pull request #241 from jgrewe/data_tag_unit

Add unit support for DataTags ...

LGTM ;-)