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This makes it easier for us to deal with arbitrary information at the
top, and means that headers added by specific commands don't overwrite
the default ones.

Add the fingerprint back, but broken up so it fits even on sprout's
display.

Change-Id: Id71da79ab1aa455a611d72756a3100a97ceb4c1c

Change-Id: Ie77a5584e301467c6a5e164d2c62d6f036b2c0c0

Everyone's adding secret key combinations for this anyway, and it's
very useful when debugging.

Change-Id: Iad549452b872a7af963dd649f283ebcd3ea24234

The current abstract class was a nice idea but has led to a lot of
copy & paste in practice. Right now, no one we know of has any extra
menu items, so let's make the default menu available to everyone.

(If we assume that someone somewhere really does need custom
device-specific menu options, a better API would let them add to
our menu rather than replacing it.)

Change-Id: I59f6a92f3ecd830c2ce78ce9da19eaaf472c5dfa