added initcube.
clean up
two cubes now
fixed a bug in leapfrog and draw
optimized but not speedup :((((

1. changed to vector<particle*>
2. used map
3. added timing
changed vector cocat in get neighbor
fixed glitch in viscosityKernelLab
fixed a typo
fixed ngbr does't contain self problem

switched back to reference from ptr
cleaned solution
temp
works in debug not release