Small improvements

app/src/dummy/java/eu/faircode/email/Send.java

@@ -29,7 +29,7 @@ public class Send {
     static final String DEFAULT_SERVER = "";
 
     public static String upload(InputStream is, DocumentFile dfile, int dLimit, int timeLimit, String host, IProgress intf) {
-        return null;
+        throw new NotImplementedException("Send");
     }
 
     public interface IProgress {

app/src/dummy/java/eu/faircode/email/VirusTotal.java

@@ -32,18 +32,19 @@ public class VirusTotal {
     static final String URI_PRIVACY = "";
 
     static String getUrl(File file) {
-        return null;
+        throw new NotImplementedException("VirusTotal");
     }
 
     static Bundle lookup(Context context, File file, String apiKey) {
-        return null;
+        throw new NotImplementedException("VirusTotal");
     }
 
     static String upload(Context context, File file, String apiKey) {
-        return null;
+        throw new NotImplementedException("VirusTotal");
     }
 
     static void waitForAnalysis(Context context, String id, String apiKey) {
+        throw new NotImplementedException("VirusTotal");
     }
 
     public static class ScanResult implements Parcelable {