added xml parse operator to parse and pick values from xml nodes and attributes

Squashed commit of the following:

commit 4d36c59484ef91b2b84986e8d0282bfa0777cec0
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Mon Jan 6 20:10:56 2014 -0800

    added more optimization

commit 0f4136183ff84cb676619bbbeb17c600b99fff0a
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Mon Jan 6 20:10:26 2014 -0800

    renamed string reader class and added public access

commit 47d8c47c399b656a526578738377d1264a7408cb
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Fri Jan 3 20:28:18 2014 -0800

    optimized logic

commit e0fad93180fb429ea5353c582a51758e573f5814
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Fri Jan 3 20:27:52 2014 -0800

    added latest xerces library for xml parsing

commit acf5b5a0a9554076d29059bd4ccbd62b0a470019
Merge: 54b51d6 54cc236
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Fri Jan 3 14:56:37 2014 -0800

    Merge branch 'telecom' of https://github.com/DataTorrent/Malhar into xmlparser

commit 54b51d685815bad40d2346f3edb431855bdeaf69
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Fri Jan 3 14:55:30 2014 -0800

    warnings and imports

commit 26aaf01bb4f3ef65b4620d856a107da0d83cfac5
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Fri Jan 3 14:39:46 2014 -0800

    added test for XMLParseOperator

commit 737ff57f677627f2c5aad316d6657c04ce42e0c1
Author: Ashwin Chandra Putta <ashwin@datatorrent.com>
Date:   Thu Jan 2 15:39:39 2014 -0800

    added xml parse operator