ENGINES: Introduce method Engine::initializePath which sets up SearchMan.

This replaces the hardcoded addition of the game path in runGame in
base/main.cpp by an engine configurable one.
TINSEL: Take advante of Engine::initializePath.

This makes sure that the game path is only ever added once for the PSX version
of DW1. Most noticably this will make the warning about the game path being
present in SearchSet disappear on startup.
Merge pull request #423 from lordhoto/engine-path-setup

ENGINES: Make game path addition to SearchMan fully configurable