Special white-space chars in IDML are protected as tags in Okapi - no match with whitespace in translate5

Special whitespace chars of IDML are protected as inline tags by okapi.

translate5's xliff import expects them as whitespace to be able to protect them as whitespace-tag and then have a matching with whitespace in the TM of t5memory.

This must be changed in Okapi, so that Okapi does not protect them anymore.

This has been implemented in Okapi with

 IDML Filter: Special characters (#1193 in Okapi)

The changed possibilies will be released with Okapi 1.46 and need to be adapted in translate5.

By default in the future in translate5 all whitespaces of IDML should not be protected as tags anymore by okapi, but by translate5 itself, so that the matching in the TM works the translate5 way and that the whitespace is identifiable in translate5.

The setting should be editable in the GUI with the following text:

EN: Protect listed whitespace characters (Important: Do NOT use in translate5 - see tooltip)
DE: Aufgelistete Whitespace-Zeichen schützen (Wichtig: NICHT in translate5 verwenden - siehe Tooltip)

And the following text in the tooltip:

EN: The whitespace needs to be left unprotected in the initial file format conversion from IDML to Xliff. The reason: translate5 needs to be able to protect the whitespace in the translate5 way for correct TM matching, instead in the Okapi way (Okapi is used for conversion from IDML to Xliff under the hood in translate5).

DE: Der Whitespace muss bei der anfänglichen Dateiformatkonvertierung von IDML nach Xliff ungeschützt bleiben. Der Grund: translate5 muss in der Lage sein, die Whitespaces auf die translate5-Art zu schützen, um einen korrekten TM-Abgleich zu ermöglichen, und nicht auf die Okapi-Art (Okapi wird für die Konvertierung von IDML nach Xliff unter der Haube von translate5 verwendet).

Also we need to make sure, that the new special whitespace tags in translate5 have each their own symbol on the tag, so that they are distiguishable. And they should be addable via our special chars section to a segment by an additional menu providing that kind of whitespace characters, see screenshot. List of characters must be delivered from the Backend since the chars are hardcoded in Whitespace.php class