Updated lua functions and lua documentation ...

ATTENTION PLEASE NOTE THAT THE FOLLOWING LUA FUNCTIONS HAVE CHANGED:
vector.Set(vec,x,y,z) -> vector:Set(x,y,z)
vector.Length(vec) -> vector:Length()
vector.Normalize(vec) -> vector:Normalize()
vector.NormalizeFast(vec) -> vector:NormalizeFast()
vector.Add(a, b, result) -> vector:Add(b) returning result
vector.Subtract(a, b, result) -> vector:Subtract(b) returning result
vector.Scale(a, scale_factor, result) ->  vector:Scale(scale_factor)
returning result
vector.Clear(vec) -> vector:Clear()
YOU MIGHT HAVE TO ADJUST YOUR LUA CODE ACORDINGLY!