title: Axes at minimum extent, no padding, in plots of raster* objects
body: <p>Is there a way to ensure that the box around a plot matches the raster extents exactly? In the following there is a gap above and below or to the left and right of the raster depending on the device proportions:</p>
  
  <pre><code>require(raster)
  r = raster()
  r[]= 1
  plot(r, xlim=c(xmin(r), xmax(r)), ylim=c(ymin(r), ymax(r)))
  </code></pre>
  
  <p>One element of the problem with raster objects is that <code>asp=1</code> to ensure proper display. The following basic scatterplot has the same issue when <code>asp=1</code>:</p>
  
  <pre><code>plot(c(1:10), c(1:10), asp=1)
  </code></pre>
  
  <p>Try <code>vectorplot(r)</code> from the rasterVis package to see what I want the axes to look like.</p>
  
  <p>EDIT:</p>
  
  <p>Solutions need to play nice with SpatialPoints overlays, not showing points outside the specified raster limits:</p>
  
  <pre><code>require(raster)
  require(maptools)
  
  # Raster
  r = raster()
  r[]= 1
  
  # Spatial points
  x = c(-100, 0, 100)
  y = c(100, 0, 100)
  points = SpatialPoints(data.frame(x,y))
  
  plot(r, xlim=c(xmin(r), xmax(r)), ylim=c(ymin(r), ymax(r)))
  plot(points, add=T)
  </code></pre>