Merge branch '617-crypto-labels' into 'master'

...briarproject/bramble/api/contact/ContactExchangeTask.java

.../org/briarproject/bramble/api/crypto/CryptoComponent.java

...g/briarproject/bramble/api/crypto/KeyAgreementCrypto.java

.../org/briarproject/bramble/api/crypto/TransportCrypto.java

.../java/org/briarproject/bramble/api/identity/AuthorId.java

...oject/bramble/api/keyagreement/KeyAgreementConstants.java

...ect/bramble/api/keyagreement/KeyAgreementTaskFactory.java

.../main/java/org/briarproject/bramble/api/sync/GroupId.java

...ain/java/org/briarproject/bramble/api/sync/MessageId.java

...riarproject/bramble/api/transport/TransportConstants.java

...briarproject/bramble/contact/ContactExchangeTaskImpl.java

.../org/briarproject/bramble/crypto/CryptoComponentImpl.java

...in/java/org/briarproject/bramble/crypto/CryptoModule.java

...g/briarproject/bramble/crypto/KeyAgreementCryptoImpl.java

...iarproject/bramble/crypto/StreamEncrypterFactoryImpl.java

.../org/briarproject/bramble/crypto/TransportCryptoImpl.java

...arproject/bramble/keyagreement/KeyAgreementConnector.java

...briarproject/bramble/keyagreement/KeyAgreementModule.java

...iarproject/bramble/keyagreement/KeyAgreementProtocol.java

...ect/bramble/keyagreement/KeyAgreementTaskFactoryImpl.java