Implementation of a framework which supports addition of contraction techniques for pgRouting.

Contraction is a technique used to speed up shortest-path computation by first creating contracted versions of the network. There are different ways of contracting a network. I am proposing a framework which supports the addition of new contraction techniques, and two contraction algorithms: dead end contraction and linear contraction. Installation of the framework together with the dead end contraction and also the implementation of linear contraction which will be used to refine the framework is intended to be completed during the GSoC.