Possible improvements to contrib

These routines are work in progress. I still need to:

Extend the FACTOR method ode1_factor to work for multiple roots.
Extend the FACTOR method ode1_factor to attempt to solve higher order factors. At present it only attemps to solve linear factors.
Fix the LAGRANGE routine ode1_lagrange to prefer real roots over complex roots.
Add additional methods for Riccati equations.
Improve the detection of Abel equations of second kind. The exisiting pattern matching is weak.
Work on the Lie symmetry group routine ode1_lie. There are quite a few problems with it: some parts are unimplemented; some test cases seem to run forever; other test cases crash; yet others return very complex "solutions". I wonder if it really ready for release yet.
Add more test cases.