It was annoying that "Entry - Appear" animation was always added
despite user had selected another effect. Correct the design as:
- "Entry - Appear" is added for the first animation in the slide.
- Last selected effect is added.
- If the category is selected but the effect isn't, the first effect
  in the category is added.

Change-Id: I5e781feb0468bef4a5e46fd277554ddeadbcfbec
Reviewed-on: https://gerrit.libreoffice.org/67977
Tested-by: Jenkins
Reviewed-by: Mark Hung <marklh9@gmail.com>