Merge branch 'key-pair-refactoring' into 'master'

...ava/org/briarproject/bramble/api/client/ClientHelper.java

...in/java/org/briarproject/bramble/api/contact/Contact.java

.../org/briarproject/bramble/api/contact/PendingContact.java

.../briarproject/bramble/api/crypto/AgreementPrivateKey.java

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

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

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

...ain/java/org/briarproject/bramble/api/crypto/KeyPair.java

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

...n/java/org/briarproject/bramble/api/crypto/PublicKey.java

.../briarproject/bramble/api/crypto/SignaturePrivateKey.java

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

...va/org/briarproject/bramble/api/db/DatabaseComponent.java

...in/java/org/briarproject/bramble/api/identity/Author.java

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

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

...rg/briarproject/bramble/api/identity/IdentityManager.java

...va/org/briarproject/bramble/api/identity/LocalAuthor.java

...rc/test/java/org/briarproject/bramble/test/TestUtils.java

...ava/org/briarproject/bramble/client/ClientHelperImpl.java