Components are more reusable when they have minimal state and/or dependency on outside resources. This commit raises the rpc calls to `ActivitiesScreen` which has the responsibility for managing the data flow and interactions between components. This update also fixes a few bugs: - Tapping an activity chip will start the activity if it doesn't have any tags. - The switches now update automatically after an activity is started or stopped. closes thehale/SimpleTimeTracker-WearOS#12 closes thehale/SimpleTimeTracker-WearOS#13