JavaDoc BaseL10n.addL10nSubstitution():

The reason for me working on fred with this one is that I've observed myself to have searched for example of how to do a bold substitution for numerous times in the JavaDoc there, so it was time to fix the JavaDoc. Did some more improvements while I was at it, see commit message.

NOTICE: My fred-commits will be GnuPG-signed from now on. Use "git log --show-signature" to verify the signature. WOT and FT commits won't be signed: I maintain the repositories myself so I have direct push access anyway. Instead once I want the fred-maintainer to publish a WOT/FT build, I will push a signed tag as usual.