Rename object to nameable

...g/briarproject/briar/android/blog/BlogControllerImpl.java

.../briarproject/briar/android/contact/ConversationItem.java

...briarproject/briar/android/forum/ForumControllerImpl.java

...ndroid/privategroup/conversation/GroupControllerImpl.java

.../org/briarproject/briar/api/messaging/PrivateRequest.java

...org/briarproject/briar/api/messaging/PrivateResponse.java

...r/privategroup/invitation/GroupInvitationManagerImpl.java

...va/org/briarproject/briar/sharing/SharingManagerImpl.java

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

...ivategroup/invitation/GroupInvitationIntegrationTest.java

...ivategroup/invitation/GroupInvitationManagerImplTest.java

...riarproject/briar/sharing/BlogSharingIntegrationTest.java

...iarproject/briar/sharing/ForumSharingIntegrationTest.java