Support Metric Names with "special characters" for Column Chooser Drag&D...

!!! please check if this right way to do it.
... column names containing special characters (for me in german translation greek "average" sign) did not work in Drag&Drop (even though the charactor is listed to be part of Latin-1 --- after changing in Mime to UTF-8 not only the greek characters, but also "TM" works without special treatment
!!! is this valid for all platforms ?!!!

(cherry picked from commit b4d1a7d3041beec686c7262cfa65bac8cf6e2179)