title: Pandas extensive 'describe' include count the null values
body: <p>I have a large data frame composed of 450 columns with 550 000 rows.
  In the columns i have :</p>
  
  <ul>
  <li>73 float columns</li>
  <li>30 columns dates</li>
  <li>remainder columns in object</li>
  </ul>
  
  <p>I would like to make a description of my variables, but not only describe as usual, but also include other descriptions in the same matrix. At the final, we will have a matrix of description with the set of 450 variables then a detailed description of:
  - dtype
  - count
  - count null values
  - % number of null values
  - max
  - min
  - 50%
  - 75%
  - 25%
  - ......</p>
  
  <p>For now, i have juste a basic function that describe my data like this :</p>
  
  <pre><code>Dataframe.describe(include = 'all')
  </code></pre>
  
  <p>Do you have a function or method to do this more extensive descrition.</p>
  
  <p>Thanks.</p>