Warning correction

Corrected the warning that came with the incomplete implementation of
PRYVApiClient
Unit Testing Enabled

Added possibility of Logic Testing and Application Testing. Ready to
code the tests methods for both logic and applicationg testing.
Rewrite of code

- Consistence with {
- Consistence with (
- Reduced length of too long lines
- Renamed instance variables adding _ in front of name
Privatisation of needed methods

Added Class Extensions to establish private methods
Model redefined

Changed the strucutre of events. The files are now attached to an Event
– and not anymore to a FileEvent. The reason is that it is very likely
that in the future, we will be able to add files to a note.
Code factorization and organization

Factored and organized the code in FileController so that is it eaiser
to read.
Service to pryv file(s) from the Finder

When the application is installer, a service is automatically added to
the finder so that it is possible to pryv files using the contextual
menu and a keyboard shortcut.
Update README.md

Added troubleshoot for the pryv file(s) service.