Flexitest MCQ image feedback

+add various image to project
Widget add default config

+childCfg attr to AddChildWidgetAction
childType still valid
+Flexitest center fix-point
Merge branch 'master' of github.com:Heigvd/Wegas

# By Benjamin Gerber (1) and Francois-Xavier Aeberhard (1)
# Via Benjamin Gerber (2) and Francois-Xavier Aeberhard (1)
* 'master' of github.com:Heigvd/Wegas:
  gauge improvement
  Fix #244 & #246