updated and added new Utils (#9)

* added SeedRandomGenerator

* extended IotaUnitConverter

* minor

* added isArrayOfHashes

* renamed constants

* added error package

* added transactionObject

* fixed IotaUnitConverter

src/main/java/jota/utils/SeedRandomGenerator.java

@@ -0,0 +1,20 @@
+package jota.utils;
+
+import java.util.Random;
+
+/**
+ * Created by pinpong on 13.12.16.
+ */
+public class SeedRandomGenerator {
+
+    public static String generateNewSeed() {
+        char[] chars = Constants.TRYTE_ALPHABET.toCharArray();
+        StringBuilder builder = new StringBuilder();
+        Random random = new Random();
+        for (int i = 0; i < Constants.SEED_LENGTH_MAX; i++) {
+            char c = chars[random.nextInt(chars.length)];
+            builder.append(c);
+        }
+        return builder.toString();
+    }
+}