Refactor the contact class

[sephorah]

Description

We created a class named FullContact, which regroups the classes ContactFile, ContactFolder, Contact, ManageContact and Computing.

We did this because the Contact class was too long and had functions which were not directly related to the Contact class.
ContactFile, ContactFolder and ManageContact have all the functions regarding the files, the folders and the contacts management respectively.

We also moved the Computing class in FullContact.

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the needed labels
• I have linked this PR to an issue
• I have linked this PR to a milestone
• I have linked this PR to a project
• I have tested this code
• I have added / updated tests (unit / functionals / end-to-end / ...)
• I have updated the README and other relevant documents (guides...)
• I have added sufficient documentation both in code, as well as in the READMEs