Add file helpers

[helrond]

Is your feature request related to a problem? Please describe.

Many of the microservices (and Aurora) use common functions to do things on the filesystem, like removing a file or directory, unzipping a bag, etc. There is a lot of duplicated code which could probably be removed.

Describe the solution you'd like

Add a file_helpers module to asterism, which includes all the commonly used functions. This will require some research to come up with a set of functions and make sure inputs and outputs are aligned across apps.