title: Plot pandas dataframe with subplots (subplots=True): Place legend and use tight layout
body: <p>I really like pandas to handle and analyze big datasets. So far, I have mostly used matplotlib for plotting but now want to use pandas own plot  functionalities (based on matplotlib) since it needs less code and seems to be sufficient for me in most cases. Especially the subplots to have a guick glance at big dataframes like in the following example..</p>
  <pre><code>import pandas as pd
  import numpy as np
  import matplotlib.pyplot as plt
  
  # Generate random data
  df = pd.DataFrame(np.random.randn(96,12),
                    columns=['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
                             'K', 'L'])
  
  # Plotting
  df.plot(kind='line', subplots=True, grid=True, title=&quot;Sample Data (Unit)&quot;,
          layout=(4, 3), sharex=True, sharey=False, legend=True,    
          style=['r', 'r', 'r', 'g', 'g', 'g', 'b', 'b', 'b', 'r', 'r', 'r'],
          xticks=np.arange(0, len(df), 16))
  </code></pre>
  <p><a href="https://i.stack.imgur.com/B4gBn.png" rel="noreferrer"><img src="https://i.stack.imgur.com/B4gBn.png" alt="enter image description here" /></a></p>
  <p>..which brings me to my questions:</p>
  <p>1.) How can I place all legends in the subplots at the same place (e. g. centered, outside, topright)?</p>
  <p>2.) Can I somehow use matplotlibs &quot;Tight Layout&quot; (<a href="http://matplotlib.org/users/tight_layout_guide.html" rel="noreferrer">http://matplotlib.org/users/tight_layout_guide.html</a>) for the plot?</p>
  <p>Thanks in advance!</p>