add IDs to note and changeset mail subjects

[Strubbl]

It would be very cool to have the note ID in the subject of emails, when a note was updated. This would also be helpful for changeset mails. I only did update the locale file for en, because i do not know where and how this needs also adjustments in the code to fill the ID place holders with the actual ID. This shall at least give an idea of i want to achieve.

At the moment the ID is only given indirectly via the noteurl or changeset_url in the user_mailer.rb. Is it anyhow easily possible to access the ID directly in the corresponding notification functions? Would it be ok for you to improve the mail subject to contain the ID?