Resolve "config application does not answer in case of some yml config duplicated names"

Closes #1464 (closed)

Improvements on this MR:

1. The web application now starts and reloads without exceptions
2. Wrong yaml or misconfiguration is shown with a warning icon on the file and a tooltip explains the kind of problem.
3. Static class was added with a kwargs boolean to allow silent exception, this is used currently only by the web configuration application and is considered safe as, even if CONFIG is a global variable, web_config is a separate process and has his own way to display errors.
4. On startup Tango Databaseds still raises exception if there is any yaml problem. Could be a further improvement, if wanted, to allow failures also on this.