mime: create more general InputDataOperation, which for now and does basic mime parsing

OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpDecryptVerifyInputParcel.java

@@ -86,10 +86,20 @@ public class PgpDecryptVerifyInputParcel implements Parcelable {
         return mInputBytes;
     }
 
+    public PgpDecryptVerifyInputParcel setInputUri(Uri uri) {
+        mInputUri = uri;
+        return this;
+    }
+
     Uri getInputUri() {
         return mInputUri;
     }
 
+    public PgpDecryptVerifyInputParcel setOutputUri(Uri uri) {
+        mOutputUri = uri;
+        return this;
+    }
+
     Uri getOutputUri() {
         return mOutputUri;
     }