public String getVersionLabel() returns the version label of
      the document.
    Parameters
None
Returns
Returns a String representing the version label of the document.
Example
    Document doc = getTestDocument(session);
    
    Log.d(TAG, "getContentStreamLength: " + doc.getContentStreamLength());
    Log.d(TAG, "getContentStreamMimeType: " + doc.getContentStreamMimeType());
    Log.d(TAG, "getVersionLabel: " + doc.getVersionLabel());
    Log.d(TAG, "isLatestVersion: " + doc.isLatestVersion());        
      
      Would result in the following output:
    getContentStreamLength: 1384691
    getContentStreamMimeType: image/jpeg
    getVersionLabel: 1.0
    isLatestVersion: true