This dictionary is important as it gives the ability to put certificate constraints on a signature field, like if you want signatures that are signed by a specific issuer or authority to only be used in a field.
currently tested Issuer constraint and it worked, acrobat reader ignores other certificates and only allow the issuer given to sign the field. documentation is not complete waiting for the initial acceptance to complete.
new class PDSeedValueCertificate is added which refers to this certificate.
PDSeedValue is modified to add the new dictionary.
COSName is modified to add the new pdf names that are included in the dictionary.
reference for this dictionary can be found in PDF reference 1.7 section 184.108.40.206 table 235 page 457 in here http://www.adobe.com/content/dam/acom/en/devnet/pdf/PDF32000_2008.pdf
or chapter 8 table 8.84 page 700 in here http://archimedespalimpsest.net/Documents/External/pdf_reference_1-7.pdf
this is my first contribution, hope everything goes well.