added tested scatterv and gatherv examples in the sub-dir

Although derived datatype approach still has problems. It's complicated package.

I adopt the easier approach of scattering and gathering multiple numbers, with default MPI datatypes. However, send and receive derived data type works...
1. implemented distribution paradigm with variable array length, using scatterv and gatherv. Although derived datatype does not work....

2. fixed the bug of not preserving particle hole symmetry... wierd bug from Gamm2 update. Need more investigation