wip bramble sharing client

...project/briar/api/mailbox/MailboxIntroductionManager.java

...java/org/briarproject/briar/BriarCoreEagerSingletons.java

...src/main/java/org/briarproject/briar/BriarCoreModule.java

...ain/java/org/briarproject/briar/mailbox/AbortMessage.java

...ect/briar/mailbox/AbstractMailboxIntroductionMessage.java

...rg/briarproject/briar/mailbox/AbstractProtocolEngine.java

.../org/briarproject/briar/mailbox/ContactAcceptMessage.java

...org/briarproject/briar/mailbox/ContactRequestMessage.java

...n/java/org/briarproject/briar/mailbox/DeclineMessage.java

.../main/java/org/briarproject/briar/mailbox/Introducee.java

...ava/org/briarproject/briar/mailbox/IntroduceeSession.java

.../java/org/briarproject/briar/mailbox/IntroduceeState.java

.../org/briarproject/briar/mailbox/MailboxAcceptMessage.java

...va/org/briarproject/briar/mailbox/MailboxAuthMessage.java

...project/briar/mailbox/MailboxIntroductionManagerImpl.java

...briarproject/briar/mailbox/MailboxIntroductionModule.java

...org/briarproject/briar/mailbox/MailboxProtocolEngine.java

...ain/java/org/briarproject/briar/mailbox/MailboxState.java

...n/java/org/briarproject/briar/mailbox/MessageEncoder.java

...va/org/briarproject/briar/mailbox/MessageEncoderImpl.java