Implement event logs component.

It can show:

 - all events (this could get slow);
 - a single sequence;
 - a set of sequences;
 - a single date;
 - a range between two dates.

It does not (yet) do pagination and filtering is local only.

lib/www/client/source/src/router/index.js

@@ -96,7 +96,12 @@ Vue.use(VueRouter)
       },
       {
         path: "log",
-        component: Log
+        component: Log,
+        children: [
+          { path: "sequence/:sequence", name: "logBySequence" },
+          { path: "date/:date0", name: "logByDate" },
+          { path: "date/:date0/:date1", name: "logByDates" }
+        ]
       },
       {
         path: "map",