Several minor improvements#5

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filbo wants to merge 9 commits intodoozan:masterfrom

Commits on Mar 18, 2014

- Use $IMAGE_FILE instead of NookManager.img, makes ad hoc testing easier
filbo
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- Report whether battery is Charging, Discharging, Not charging, Full.
filbo
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Commits on Mar 20, 2014

- Fix % battery message in case where we can't read the charging state.
filbo
committed