compatibility: gnumeric allows characters in sheet names not accepted by Calc and Excel,
See https://bugs.documentfoundation.org/show_bug.cgi?id=142297
Calc won't allow: empty names, already existing, characters [, ],
*, ?, :, /, \ and ' ( apostrophe ) as first or last character.
Excels restrictions are different, tool-tip, help and actioning
out of sync, add. not allowing <, >, " and |.
Think disabling would break internal back-compatibility?
should we issue a warning 'using exotic characters may cause
problems in compatibility to other programs!' when such names
are chosen??