pldata.blob.Blob.compare: remove noisy log messages
pldata.mkvcomblob: fix bug with variable name
pldata.mkwfblob: return --check result
pldata.mk{vcom|wf}blob: fix log messages when running --check
pldata.blob: add VermagicEntry for version and magic

Add VermaticEntry to add a fixed version or magic value
to a blob.  This will always pack the same value and raise
an error if a different value is unpacked (the fixed value
is passed to __init__ and can be anything).
pldata.mk{vcom|wf}blob: use VermagicEntry

Use VermaticEntry for all version and magic values so an exception
will now be raised if unexpected values are found.
pldata.mk{vcom|wf}blob: return error code upon exception
ChangeLog v005 -> v006