Message will render as user is scrolling down. This prevents interface freezes on long messages (such as inline img in text mode). Fixes Bitmessage##366 Also a minor fix in text mode rendering.
Links in message body (if in HTML mode) now open, but it asks for a confirmation in a dialog box. Fixes #27
HTML messages are detected and if present, the top of the message textedit displays a clickable area that switches HTML rendering on and off. Fixes #13
