Page 21 of "PAdES baseline signatures" specification from
<http://www.etsi.org/deliver/etsi_en/319100_319199/31914201/01.01.01_60/en_31914201v010101p.pdf>
says:

"The Signature Dictionary shall contain a value of ETSI.CAdES.detached
for the key SubFilter."

So in case the UI has the adescompliant checkbox enabled, write that
value instead of the Adobe default.

Change-Id: I69e606a32fb09bebd5e9b25b32150d1b8672f544