1. convertAnimationValue convert the attribute value of a animation
target from MS ppt to the format that slideshow understand,
moving it so that it can be resued in oox.

2. convertMeasure is used by convertAnimationValue, moving it togehter
eliminate the duplicated function in oox.

Change-Id: I41cd1cf731b6496d7ae96b174a1748326415593f
Reviewed-on: https://gerrit.libreoffice.org/57287
Tested-by: Jenkins
Reviewed-by: Mark Hung <marklh9@gmail.com>