sd_fusing.py: Refactor parameters writing

sd_fusing.py: Refactor parameters writing

This commit considerably alters when and which parameters are written
to "inform" partition:

 - Parameters are now updated always, not only when --format has been
   specified (this is compatible with old sd_fusing.sh behaviour)

 - Initial parameters are collected from configuration and from user
   input to reflect actual flashing options, eg. if user chosen to
   update only 'a' partition script won't set the flag that both
   partitions are cloned

   Dynamic parameters generation allowed to drop a lot of duplicated
   params.

Change-Id: I597f104b2b7972728663e2d85555407c721b7bb0
Signed-off-by: Karol Lewandowski <k.lewandowsk@samsung.com>