Help, print, and exception messages will now all be translated. I
did not find any logging messages.
Motivation for this change:
1. A patch for shell.py recently added i18n, we should be
consistent with the additions from v1.
2. I noticed a patch on v1/shell.py that had reviewers suggesting
to use i18n, instead of applying it to one message lets do it
for the whole file.
Change-Id: Ifd1bf25020c5f180a074165e2634a105bcbd4ed8