Stop trimming leading/trailing whitespaces on segment save

Trailing/leading whitespaces are preserved on task import, but are trimmed on segment save.

This leads to that the following test failes, as repetitions are counted differently

Translate1475Test::testSegmentEditing: 
- 'isRepeated' => '3' 
+ 'isRepeated' => '1'

Trimming of trailing/leading whitespaces was introduced at the point of time when we had a bug years ago, where browsers did insert that. Perhaps in certain scenarios, if tags are at the start or end of the segment, or something similar. So we need to check whether it's still like that and if no - stop trimming