special purpose contacts

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

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

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

...va/org/briarproject/bramble/api/contact/ContactTypes.java

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

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

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

.../org/briarproject/bramble/contact/ContactManagerImpl.java

...e/src/main/java/org/briarproject/bramble/db/Database.java

...va/org/briarproject/bramble/db/DatabaseComponentImpl.java

...c/main/java/org/briarproject/bramble/db/JdbcDatabase.java

.../briarproject/bramble/contact/ContactManagerImplTest.java

...rg/briarproject/bramble/db/DatabaseComponentImplTest.java

.../org/briarproject/bramble/db/DatabasePerformanceTest.java

...st/java/org/briarproject/bramble/db/JdbcDatabaseTest.java

...iarproject/briar/android/contact/ContactListFragment.java

...droid/contactselection/ContactSelectorControllerImpl.java

...rproject/briar/introduction/IntroduceeProtocolEngine.java

...java/org/briarproject/briar/test/TestDataCreatorImpl.java

...oject/briar/introduction/IntroductionIntegrationTest.java