Bug 251435 - Populate translation hints if string has no translations

- Fix regression from comment 10
- Make the hints condidional to there being no existing translation
- Add Bold to the hints header, to better separate the header from hints

Change-Id: I1ca323037c272fc6bdba3e50457df0dea80bf6b6
Signed-off-by: droy <denis.roy@eclipse-foundation.org>