check if an aggregate complete transaction has all cosignatories

[khawarizmus]

From this doc issue we need a method that given an Aggregate complete transaction needs to check if this transaction has all cosignatories required and ready to be announced

An Aggregate Complete Transaction has to know if he has all the required cosignatures, up to date, it's developer responsibility to know and check the cosignatures in a manual way. We should create a method in the nem2-sdk that given an ACT, check if it has all the required cosigners automatically.

isComplete(signedAggregateCmpleteTransaction: SignedTransaction): boolean;

Summary of requirements

• Create an easier way to re-create the ACT.
• Serialization
• Check ACT status with chain information

Because it requires network results, we will need to create a service that leads to all network calls.

Also, we need an Aggregate Transaction instead of SignedTransaction, we could get more information about the Aggregate Transaction since SignedTransaction does not contain all the information or it's serialized and more difficult to read.

[rg911]

this is depend on PR #86 to be merged first

[dgarcia360]

@rg911 Here you have a specification to test this issue before merging:

• Success: https://github.com/nemtech/nem2-scenarios/blob/master/features/escrow/create_an_escrow_contract.feature#L33-L76
• Failure: https://github.com/nemtech/nem2-scenarios/blob/master/features/escrow/create_an_escrow_contract.feature#L176-L216