adds clear log button to menu

- clear log now static function, with
  the log being updated from file
  every time the update function is called
- menu actions always act from main activity
  so the menu isn't able to use the existing
  bump instance

app/src/main/res/values/strings.xml

@@ -1,6 +1,7 @@
 <resources>
     <string name="app_name">Bump</string>
     <string name="action_settings">Settings</string>
+    <string name="action_clear_log">Clear Log</string>
     <!-- Strings used for fragments for navigation -->
     <string name="main_fragment_label">Bump</string>
     <string name="second_fragment_label">Second Fragment</string>