List time alert

The creator of a form will have the ability to define an 'observation_list_time_length' variable in the form header. It is a time in seconds, and means that the user should create a list of this form in x seconds. The ListTimerAlertHandler component is a viewless component which handles these data, and alerts the user to finish the list creation minutes before the end, and at the end of that time. If the user opens the app in the interval of and , the first alert will show as well. But, after the , only the final alert will be scheduled. These to constants are now static, 5 minutes and 2 minutes. If the API changes then it can be modified to anything the API tells the app.

issue #85 (closed)