Revert "user plain pointers for Effect, this fixes a segfault due to double delete when using more than one EffectRack"

This reverts commit 2454bb037ceb79726a983ff4b57345beae53f8f5.

Conflicts:
	src/effects/effect.cpp
	src/effects/effectchain.cpp
	src/effects/effectchain.h
	src/effects/effectchainslot.cpp
	src/effects/effectchainslot.h
	src/effects/effectparameter.cpp
	src/effects/effectsbackend.cpp
	src/effects/effectsbackend.h
	src/effects/effectslot.cpp
	src/effects/effectslot.h