[Tizen] Check signature value using xmlsec1 library

Based on API provided by xmlsec1 library, signature value and reference
are checked.
Actually in signature.xml, there will include a few certificates, which forms a certificate chain. After parser each certificate, we can extract "subject" and "issuer" information. The subject of parent should be the issuer of the child. In order to verify signature, we have find all certificates in the chain.  Widget built from Tizen SDK, the root certificate is not included in the certificate chain.  So I need get the root certificate by subject which is the last issuer of including certificate chain.