Support animated PDF

With this patch we can execute animations from the Beamer and animate packages for Latex. It needs Poppler with version > 0_79 to work.

Some functions in forms were added to support the display features in the reference, namely the printable/setPrintable functions, also we needed to support changing the appearance of the form.

The setInterval/clearInterval() is used with QTimers to call the script in a interval. I'm deleting these timers when clearInterval is called or when the interpreter is destroyed. I couldn't figure out a way to store the timers and restore them, that's why I'm storing their IDs in a Hash and getting them back later.

The getOCGs uses the layersModel already implemented on Okular sidebar, I just transfer it's useful information into an object.

Also I made changes to execute some scripts on the page Opening, the widgets script code should be executed.

To test:

Any of the http://www.texample.net/tikz/examples/tag/animations/ for beamer.

animate.pdf for animate Package.

Fixes:

#403772

#242617