Cleanup in code: Removed unused directives from all DocX files

DocX/Container.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 using System.Text.RegularExpressions;
 using System.IO.Packaging;

DocX/CustomProperty.cs

 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
 namespace Novacode
 {

DocX/DocProperty.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Xml.Linq;
+using System.Xml.Linq;
 using System.Text.RegularExpressions;
 
 namespace Novacode

DocX/Footer.cs

 using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 using System.IO.Packaging;
 

DocX/Footers.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-
-namespace Novacode
+namespace Novacode
 {
     public class Footers
     {

DocX/FormattedText.cs

 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 
 namespace Novacode
 {

DocX/Header.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 using System.IO.Packaging;
 

DocX/PageLayout.cs

 using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 
 namespace Novacode

DocX/Paragraph.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 using System.Text.RegularExpressions;
 using System.Security.Principal;
-using System.Collections;
 using System.IO.Packaging;
 using System.IO;
 using System.Drawing;

DocX/Picture.cs

-using System;
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
-using System.Drawing;
 using System.IO.Packaging;
 
 namespace Novacode

DocX/Table.cs

 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
-using Novacode;
 using System.IO.Packaging;
 using System.IO;
-using System.Reflection;
 using System.Drawing;
 using System.Globalization;
 

DocX/_BaseClasses.cs

 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Xml.Linq;
 
 namespace Novacode

DocX/_Enumerations.cs

-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-
-namespace Novacode
+namespace Novacode
 {
     public enum PageNumberFormat
     {