Add support for PSS padding when signing with RSA
Created by: visechelle
SWUpdate supports both PKCS#1 and PSS padding with RSA but swugenerator only implements PKCS#1 padding. PSS padding support is therefore added in SWUSignRSA.
One can use the keyword RSAPSS to sign the sw-description file with RSA and PSS padding. For instance:
-k RSAPSS,myprivatekey.pem