Pyfecons library

[craastad]

https://trello.com/c/JUKmKM9y/19-integrate-pyfecons-as-library

Changes:

• Add pyfecons folder to serve as library
• Add setup and initi files as library setup
• Add explicit constructors and default values for Input classes
• Use pythonic snake case for input field names
• Add Enums previously in saas-backend repo
• Add placeholder requirements.txt even though we don't have any dependencies right now