Updated poster to use CSS styles to hide instead of show/hide methods. fixes #1567

- Poster will now reshow itself when a poster source is set after a non-source
- Relying on CSS instead of show/hide methods now
- Made it so empty strings would hide the poster image element
- Updated a few component methods that made it annoying to create a mock player (@dmlap)
- Refactored poster image tests
I want answers or cook me , one way or the other this ends now , regards wayne <a href="https://overview.mail.yahoo.com?.src=iOS"><br/><br/>Sent from Yahoo Mail for iPad</a>