[mono.data.sqlite] Cleaned up source code after feedback:
 - removed the unnecessary NET_2_0 pre-processor branches
 - fixed whitespace and formatting
 - removed and reverted the DbConnectionString and DbConnectionOptions types as these are obsolete and unused
 - PropertyCollection now again correctly derives from Hashtable (which is now included in System.Data for WP/Store)
 - created xml extension methods to hide platform differences
[system.data] Skip over non-element nodes in an xml fragment (#20714)

This is what MS.NET does when loading fragments. Bug is on https://bugzilla.xamarin.com/show_bug.cgi?id=20714
[system.data] Fixed code for .NET 2.0
 - ensure that the classes come before the interfaces in the derived type lists
 - incorrectly moved a line of code in DataSet (read depth BEFORE moving the cursor)
 - removed usings
 - added a "hack"for compiling extension methods in .NET 2.0
 - corrected the Type names for XDocument and XElement
Merge pull request #3 from mattleibow/system.data-wp-fixes

System.data wp fixes
Merge branch 'system.data-wp' into mono.data.sqlite-wp