Refactor Author.Status into dedicated AuthorInfo class and add alias

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

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

...ava/org/briarproject/bramble/api/identity/AuthorInfo.java

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

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

...rg/briarproject/bramble/identity/IdentityManagerImpl.java

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

...riarproject/bramble/identity/IdentityManagerImplTest.java

...ava/org/briarproject/briar/android/blog/BlogPostItem.java

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

.../java/org/briarproject/briar/android/forum/ForumItem.java

...r/android/privategroup/conversation/GroupMessageItem.java

.../privategroup/conversation/JoinMessageItemViewHolder.java

...briar/android/privategroup/memberlist/MemberListItem.java

...android/privategroup/memberlist/MemberListItemHolder.java

...ject/briar/android/threaded/BaseThreadItemViewHolder.java

...a/org/briarproject/briar/android/threaded/ThreadItem.java

.../java/org/briarproject/briar/android/view/AuthorView.java

...g/briarproject/briar/android/view/TrustIndicatorView.java

...g/briarproject/briar/android/forum/ForumActivityTest.java