Transform: fix interpolation of \[1-4]a from \alpha.

This is a moderately bad hack that will break horribly on lines with
tags that are malformed in a specific way.

So, format your lines properly.
TrimHandler: don't try to encode dummy videos.
Aegisub-Motion: fix first-run trim config popup.

I'm certain this used to work and I'm really not sure what changed.
TrimHandler: use path specifier for temp directory.
LineCollection: set useful data with addLine.
Aegisub-Motion: move createPrefix checkbox next to prefix.
Docs: update submodule.
Aegisub-Motion: fix trim config popup for real.

I don't know how I keep screwing this up. It is spectacular.
Version bump.
LineCollection: don't perform comparison to nil in addLine.