Bug 1869: Fixed binding-data-codec to work with empty type

Bug 1869: Fixed binding-data-codec to work with empty type

Empty type is special case, which does not contain value,
but has only presence characteristic and in Binding Specification v1
it was converted to boolean (true = present, false or null not present)
but new codecs did not have that special handling for empty type
which caused some models to fail.

Fixed places affected by this bug and added test case which now
explicitly tests empty type support.

Change-Id: Idec541dc9da987cebcd46ee65d24c17b7cf9a567
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>