Implement Simple-Coin with Single Signature Template

[YaronWittenstein]

Depends on: #440 #444 #448 #452

In order to test the Simple Coin Iteration #2, we need to write a Template that will test the new support for implementing Signatures Schemes.

Notes

• The ctor of the Template should expect a PubKey as input.
• The Template should override the default verify method.

Verify Implementation

1. Get the Signature received at the sigdata of the transaction.
2. Load the PubKey from the Account's Storage. (the PubKey stored in the ctor).
3. Verify the Transaction (without the sigdata part) using the Signature (of 1.) and PubKey (of 2.)