Improve tooltip on internal space tags

With TRANSLATE-888 also tab characters are masked with a internal space tag on import.
Therefore it would be useful when the mouse over (title attribute) in the frontend shows more information about the space tag, as it is done at the moment.
Some tooltip examples:
"3 whitespace characters" when there were 4 spaces in the content. One of the whitespaces remains in the content.
"7 tabulator characters" when there were 7 tabs in the content.

Possible place for implementation:
editor_Models_Import_FileParser_TagTrait::whitespaceTagReplacer()