title: ggplot2 - Reset axis text after it's been set to element_blank
body: <p>Once someone has set the <code>axis.text</code> to <code>element_blank()</code>, can the original setting be easily recovered. By original, I mean the ggplot2 original, not the original as of the moment that <code>element_blank()</code> was set. Basically, can is there something like <code>axis.text.x = element_default()</code>?</p>
  
  <pre><code>library(ggplot2)    
  
  # A while ago in my code, someone might do this
  x = ggplot(PlantGrowth, aes(x=group, y=weight)) + 
        geom_boxplot() + 
        theme(axis.text.x = element_blank())
  
  # Is there an easy way for me to do this:
  x2 = x + theme(axis.text.x = default_ggplot2_value_for_this_item)
  </code></pre>