store element type in ParticleGroup, create PSA instance explicitly

- static object instances are difficult to handle correctly, as you can't know when there ctor will be called.
reorder folder structure
move terrain actor init to terrain generator
define sources and shaders in separate CMakeLists.txt
add destruction of LuaWrapper instance in ParticleScriptAccess
Merge pull request #113 from lanice/project_reordering

Project reordering