Mask tab character in source files with internal tag

If source files are containing one or more tab character(s) in the source or target data, this tab character(s) should be replaced with an internal tag.
Multiple tabs without any other character in between should be masked as one internal tag.
The same mechanism as for multiple space tags should be used.
The export will work out of the Box, the fix itself affects only the import. Therefore no migration script is needed.