Fix indexing nil error if the clipboard only contains a linebreak.

In this case, DataHandler:rawData is an empty table.
Don't allow nil return from fetchDataFromClipboard.

Empty strings are more friendly, probably.
Add Shake Rotoshape data sample.
Fix errors related to independent clip tracking.

HURRDURR I AM AN IDIOT
Fix alpha interpolation error.

Man, I am either sloppy or careless or both.
Deduplicate tags after transform interpolation has occurred.

Makes the resulting lines far more clean.
Add accelerators to rectClip, vectClip and killTrans.

They are `l`, `V` and `t`, respectively.
Clean up formatting of clip dialog table.
Add clipOnly option.

Allows clips to be tracked from the main dialog without moving the line.

The same behavior can be had by using the separate clip tracking
feature and either disabling all of the options in the main window or
not providing tracking data to the main window. However, this may be
more convenient for the user.
Version bump.