Include Working Set configuration to the New PyDev Project wizards.

Dedicate a section of the New PyDev Project wizards for adding the project to working sets,
as new project wizards for Java, Javascript, andi some other resource types, do. This change
affects all three PyDev project types: standard, Django, and Google App Engine.

-----------

The working set code was taken from org.eclipse.jdt.ui. To my knowledge everything works fine, despite Eclipse throwing warnings telling me that I shouldn't be referencing things from org.eclipse.jdt.