Bar/Battery: improved tooltip and handle negative charging rate

- Also slightly tweaked StyledTooltip minimum size to avoid
inconsistencies (Tooltip with a single line looked like pills instead of
rounded rectangles)

Helpers/Time.js

@@ -0,0 +1,18 @@
+function formatVagueHumanReadableTime(totalSeconds) {
+    const hours = Math.floor(totalSeconds / 3600);
+    const minutes = Math.floor((totalSeconds - (hours * 3600)) / 60);
+    const seconds = totalSeconds - (hours * 3600) - (minutes * 60);
+ 
+    var str = "";
+    if (hours) {
+        str += hours.toString() + "h";
+    }
+    if (minutes) {
+        str += minutes.toString() + "m";
+    }
+    if (!hours && !minutes) {
+        str += seconds.toString() + "s";
+    }
+    return str;
+}
+