Merge branch 'scrypt' into 'master'

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

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

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

...ava/org/briarproject/bramble/crypto/PasswordBasedKdf.java

.../main/java/org/briarproject/bramble/crypto/ScryptKdf.java

...c/test/java/org/briarproject/bramble/crypto/HashTest.java

...ava/org/briarproject/bramble/crypto/KeyAgreementTest.java

...va/org/briarproject/bramble/crypto/KeyDerivationTest.java

...riarproject/bramble/crypto/KeyEncodingAndParsingTest.java

...rc/test/java/org/briarproject/bramble/crypto/MacTest.java

...arproject/bramble/crypto/PasswordBasedEncryptionTest.java

...t/java/org/briarproject/bramble/crypto/ScryptKdfTest.java

...t/java/org/briarproject/bramble/crypto/SignatureTest.java

...iarproject/bramble/sync/SyncIntegrationTestComponent.java

...org/briarproject/bramble/test/TestSecureRandomModule.java

...rg/briarproject/briar/android/login/PasswordFragment.java

...oject/briar/feed/FeedManagerIntegrationTestComponent.java

...ar/introduction/IntroductionIntegrationTestComponent.java

.../briar/messaging/MessageSizeIntegrationTestComponent.java

...r/messaging/SimplexMessagingIntegrationTestComponent.java