Fix Animation Export Dialog.

This does two things:

1. It makes sure that the default dialog uses the encoder config you
can set for that file format. This ensures baseline is defaulted to instead
of the default ffmpeg uses.
2. It adds in a warning dialog because mp4 and mkv don't like using uneven numbers and thus
will error out ffmpeg.

Please check if this patch doesn't break your animation workflow!

CCMAIL:kimageshop@kde.org