Facade for forum post headers. #172

...oid/src/org/briarproject/android/forum/ForumActivity.java

...roid/src/org/briarproject/android/forum/ForumAdapter.java

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

...src/org/briarproject/android/forum/ForumListActivity.java

...oid/src/org/briarproject/android/forum/ForumListItem.java

...org/briarproject/android/forum/ReadForumPostActivity.java

...rg/briarproject/android/forum/WriteForumPostActivity.java

briar-api/src/org/briarproject/api/forum/ForumManager.java

...r-api/src/org/briarproject/api/forum/ForumPostHeader.java

briar-core/src/org/briarproject/forum/ForumManagerImpl.java

...-core/src/org/briarproject/forum/ForumPostHeaderImpl.java