TrackerCommand --> MeasureCommand + fuse against exception in MeasureTool dtor + added DeleteMeasureCommand + moved the various concrete measuring tool-related classes to their pre-assigned file locations (everything was crammed into MeasureCommands.* files up to this commit) + added double-click handler to GuiAdapter (for TOA implementation of "delete measuring tool on double-click")

html, body {
  width: 100%;
  height: 100%;
  margin: 0px;
  border: 0;
  overflow: hidden; /*  Disable scrollbars */
  display: block;  /* No floating content on sides */
  background-color: black;
  color: white;
  font-family: Arial, Helvetica, sans-serif;
}

canvas {
  left:0px;
  top:0px;
}