Further shared preferences and beginning to modify notifications.

src/main/java/com/example/notification/Notification.java

.../java/com/example/notification/SedentaryNotification.java

...main/java/com/example/pharmacy/frontEnd/MainActivity.java

src/main/java/com/example/pharmacy/frontEnd/Settings.java

src/main/java/com/example/stimulus/SedentaryStimulus.java