Create methods to verify if token id has already been minted or token has been spent

[martti007]

Create a isMinted and isStateSpent methods to transition client.

[b3y0urs3lf]

Tested locally using java sdk commit 7980e68 and go aggregator commit 4052d57dad5dde14493ec023394dd991216eed01.

Checked that method isMinted working and can be used for assert:

        assertTrue(this.client.isMinted(currentToken.getId(), this.trustBase).get());

Also checked that method isStateSpent working and can be used:

           assertTrue(this.client.isStateSpent(currentToken, signingService.getPublicKey(), this.trustBase).get());

Moving task to done.