Add a github-style no-flash fallback for quick copy

Basically, if the browser doesn't support flash, the button to copy is still shown currently and clicking on it obviously does nothing.

With this PR, `CopyClipboardComponent` will show a text field with the text to copy instead of a button if flash isn't supported. Clicking anywhere on this input will select all of its content and the user will be copy manually then (like on GitHub).

![screen shot 2013-09-15 at 19 34 19](https://f.cloud.github.com/assets/315596/1145624/df012b68-1e24-11e3-8d2a-3769961e0887.png)