TtFolder is used with private methods

[lbusoni]

traking_number_folder.TtFolder has a single private method that is used everywhere.
Make it public ! Or even better replace:

save = tracking_number_folder.TtFolder(store_in_folder)
dove, tt = save._createFolderToStoreMeasurements()

with:

dove, tt = tracking_number_folder.TtFolder(store_in_folder)

Also make name more explicit: TrackingNumberFolderWriter ? MakeTrackingNumberFolder ?

[ChiaraSelmi]

Modified. Changed all files in the master.
How to join these changes from master to Accelerometers branch so you can edit there too?
(see: https://www.atlassian.com/git/tutorials/merging-vs-rebasing)