Use JumpPad-specific soundscript definitions for build/explode sounds

A simple little change that allows people to customize jump pad sounds without having to alter the detpack sounds as well. Requested by R00Kie/@BleuJudou

Requires soundscript definitions that are already committed: https://github.com/fortressforever/fortressforever-scripts/commit/24438e3e4526ef33a02ab26802108f20efd34f6c