Refactor tests + Add support for asset re-issuance

[altafan]

This adds the support for creating transactions that re-issue asset.

BONUS:

• integration tests have been refactored so that the signing and the finalization/extraction/broadcasting of the transaction take place respectively into signTransaction and broadcastTransaction, in the same way as the blinding is done into blindTransaction. This, in general, to increase reliability and to remove a lot of code repetions. We should do the same for the crafting of the tx.. maybe we could create some smart functions to avoid all the repetitions of the creation of inputs/outputs and keys.
• remove nonsense integration tests and add more for different types of inputs.
• fix functions of the address package that were expecting a network as arg instead of aclling NetworkForAddress (used also as validation check for the address in this way).
• add missing tests for updater.AddIssuance method.

Closes #107.
Closes #112.
Closes #113.

Please @tiero, review this.