Testnet 0.7.3

• MakeAssetNameUnique transaction was removed
• New validation rules for CreateAliasTransaction

We've removed MakeAssetNameUnique transaction because it's considered useless. Also we've hardened alias string constraints, now it's limited to lower case ASCII letters, numbers and 4 special symbols ('.', '_', '-', '@').
Because of this we are going to restart Testnet from last valid block. Please, remove blockchain.dat and state.dat upon update.