Added utilities to work with text, xml format and urls

Added a parametrized function GenerateResponse to avoid repetitive sequences of if...elif...else

Tested this new function with the components api

Removed components.xml template
Manufacturers and Categories view changed to use the unified render

Modified inforation returned by api entry points of manufacturers and categories

	modified:   PCnsteinapp/datautils.py
	deleted:    PCnsteinapp/templates/categories.xml
	deleted:    PCnsteinapp/templates/component.xml
	deleted:    PCnsteinapp/templates/manufacturer.xml
	deleted:    PCnsteinapp/templates/manufacturers.xml
	modified:   PCnsteinapp/views.py