multi-wc-format: WC upgraded and not-upgraded notifications

Daniel Shahaf wrote, in dev@ email "multi-wc-format review":

«svn upgrade» of an f31 working copy does nothing and prints nothing. I see this is deliberate behaviour (by the docstring of SVN_WC__DEFAULT_VERSION).

[...] should «svn upgrade» print an info message to the effect of "I upgraded your wc to f31 but I can also upgrade it to f32 if you request that explicitly", so users don't mistakenly assume they're running the latest-and-greatest wc format?