`Dataset`: ArrayInterface Overload

[ax3l]

We could simplify non-MPI Python code if we add another constructor to Dataset:

import openpmd_api as io

data = np.arange(size*size, dtype=np.double).reshape(3, 3)

# now
dataset = io.Dataset(data.dtype, data.shape)

# future
dataset = io.Dataset(data)

[CODEAbhinav-art]

/assign