Add sample blog posts at app start [prep]

- Add sample data at app start to avoid having to create new blog posts manually each time the app is launched.
- Add a new post constructor for easier object creation.
Make the body field multi-line [create]

- Change the body field from textLongMessage to textMultiLine to ensure text wraps.
Add a custom adapter [session-6, post-list]

- Add a custom array adapter which returns a custom view for the blog post list.