Split out h5_create_group so it can be used by other modules.

Split out h5_create_group so it can be used by other modules.

My initial break from pypiezo was not from the pypiezo tip.  This
commit pulls in following pypiezo changes:

  commit 67d6dca84988d5d4271835522f4697d9e0a2c6f2
    Split out h5_create_group so it can be used by other modules.
  commit 9afcf604e967123b3cdf2665827afe24a74225f2
    Return the group created in h5_create_group().
  commit 5d84f6b5392236e8d2b1513178063bfc2a5f5893
    Special case for '/' group in h5_create_group.

It also strips trailing whitespace from h5config/hdf5.py.