First display test connections as lines

the code is very dirty and not functional at the moment but this is a test
first test display connections

Segmentation fault
Trying to display connection lines

Connection creation and ConnectionWrapper creation work well (they can be displayed in the console) but no connection is displayed in the window. I shouldn't have used signals well.
Merge branch 'develop' into testDisplayConnectionsExperimental
Change management of connection

- An idClip has coordinates too (think to update coordinates  after moving node)
- connectionWrapper doesn't contain the idClip anymore but only coordinates of the line extremities
- Signals to improve
- Disappearance of the lines to fix