Import animation

This combines both import video and import frames (the latter which had not gotten it's own page yet).

There's still some things unclear to me, but one thing that's really noticable is that it's UI needs a one-over:

There's random button sizes and label sizes make this a very busy UI. The import options are named export and I am unsure why there's a second options tab. And what is ffmpegprobe doing here???