Add new service 'write_blob' to 'io.HDF5Sink'
Closes #215 (closed)
Example
ablob = kp.Blob()
ablob['empty'] = None
ablob['data'] = kp.Table({ 'time': np.zeros(5) }, h5loc = '/data')
bblob = kp.Blob()
bblob['nested'] = kp.Table({ 'event': np.zeros(10) }, h5loc = '/deep/nested')
bblob['detsen'] = kp.Table({ 'tneve': np.zeros(10) }, h5loc = '/deep/detsen')
ablob['deep'] = bblob
sink = kp.io.HDF5Sink(filename = 'test.h5')
sink.write_blob(ablob)
sink.finish()