[Tizen] Add signature data and parser logic

For Tizen signature file, it is a XML, which must match Tizen signature
schema. After verifying input XML, we use SignatueData to store values
parsing from signature.xml. And the data will be used by signature verifier
to validate digital signature furthur.
Merge pull request #2169 from xuzhang/widgetsignatue

[Tizen] Add signature data and parser logic