Fix log display cosmetics

Clear app display region before restarting log UI so as to not leave
old junk behind if new font leaves leftover space at top of screen

Draw text starting one pixel below log separator lines so the line
doesn't overstrike topmost pixels of text

apps/stamplog/app.js

@@ -180,7 +180,7 @@ function renderLogItem(elem) {
      .drawString(locale.date(elem.item.stamp, 1)
                  + '\n'
                  + locale.time(elem.item.stamp).trim(),
-                 elem.x, elem.y);
+                 elem.x, elem.y + 1);
   } else {
     g.setColor(g.blendColor(g.theme.bg, g.theme.fg, 0.25))
      .fillRect(elem.x, elem.y, elem.x + elem.w - 1, elem.y + elem.h - 1);
@@ -242,6 +242,7 @@ class MainScreen {
   // Launch this UI and make it live
   start() {
     this._initLayout();
+    this.layout.clear();
     this.scroll('b');
     this.render('buttons');