evolve: move the evolve command to evolvecmd.py This patch moves finishes the code movement by moving the evolve command to evolvecmd.py.

evolve: move _orderrevs() function evolvecmd.py _orderrevs() is a function which is used to order the revs in which the instability needs to be solved if we have multiple revisions to resolve.

evolve: move builddependencies() and _singlesuccessor() to utility module The builddependencies() and _singlesuccessor() function are very useful functions and can be used at a lot of places. They are also used in topic extension also, so let's move them to utility. However moving them to utility won't help anything in the topic extension.