BLOCK_DIAGRAM: Make sure it works when running from installed path

Signed-off-by: Robin Getz <Robin.Getz@analog.com>
FMCOMMS2: Save/Restore DAC file if one is set

Signed-off-by: Robin Getz <robin.getz@analog.com>
FMCOMMS2: Tweak wording a little in the advanced tab

Signed-off-by: Robin Getz <Robin.Getz@analog.com>