title: ggplot2 outside panel border when using facet
body: <p>I would like to have a border around the outside of my faceted plot but not have the lines that separate the panels inside the plot. The issue is that panel.border draws a border around each panel in the facet with no option to just have a border around the entire plot. Alternatively can you set the inside dividing lines to 'white' but keep the outside border 'black'. </p>
  
  <p>Here is my code:</p>
  
  <pre><code>mtcars
  mtcars$manufacturer=rownames(mtcars)
  ggplot(mtcars, aes(x=manufacturer, y=mpg,fill=factor(gear,levels=c("3","4","5"))))+
    geom_bar(stat="identity",position="dodge",colour="black")+
    facet_grid(~cyl,scales = "free_x",space = "free_x",) +
    theme(axis.text.x = element_text(angle = 45,size=12,colour="Black",vjust=1,hjust=1),
      strip.background = element_blank(),
      strip.placement = "inside",
      strip.text = element_text(size=15),
      legend.position=c(0.9,0.8),
      legend.title=element_blank(),
      legend.text=element_text(size=15),
      panel.spacing = unit(0.2, "lines"), 
      panel.background=element_rect(fill="white"),
      panel.border=element_rect(colour="black",size=1),
      panel.grid.major = element_blank(),
      panel.grid.minor = element_blank())
  </code></pre>
  
  <p>Result: Faceted plot with inside borders</p>
  
  <p><a href="https://i.stack.imgur.com/huByv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/huByv.png" alt="enter image description here"></a></p>
  
  <p>Desired output (edited in paint): Faceted plot without inside lines</p>
  
  <p><a href="https://i.stack.imgur.com/gycag.png" rel="noreferrer"><img src="https://i.stack.imgur.com/gycag.png" alt="enter image description here"></a></p>
  
  <p>My actual data plot that I want to remove the inside lines from looks like this:</p>
  
  <p><a href="https://i.stack.imgur.com/tODqJ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/tODqJ.png" alt="Actual data plot with inside borders needing to be removed"></a></p>