Make some util methods private

[wtbarnes]

There are a number of functions in fiasco.util that need not be part of the public API as they are only used within one or two functions, also within fiasco.util, and have limited usefulness outside of those functions. These include:

• fiasco/fiasco/util/setup_db.py

  Line 94 in f996aea

  def check_database_version(ascii_dbase_root):

• fiasco/fiasco/util/setup_db.py

  Line 116 in f996aea

  def md5hash(path):

• fiasco/fiasco/util/setup_db.py

  Line 131 in f996aea

  def get_test_file_list():

These should be removed from the top-level fiasco.util namespace as well as prepended with a _ to denote them as private functions.