Reimplement behaviour in imag-header
Reimplement behaviour in imag-header

This patch changes imag-header to do not printing of the found values,
but simply filtering.

Chaining can then be used to read the values:

    imag ids | imag header string "imag.version" | imag header read "imag.version"

for example.

Signed-off-by: Matthias Beyer <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@beyermatthias.de>

matthiasbeyer/imag,matthiasbeyer/imag