[eigen] Add `ifopt` and `towr` to "Projects using Eigen" Documentation

[Alexander Winkler <winklera@xxxxxxx>]

I would like to mention two projects under "Projects using Eigen" on the Eigen main page. They build heavily on Eigen and are open-sourced on github:

https://github.com/ethz-adrl/ifopt

https://github.com/ethz-adrl/towr

If this is a reasonable request, how can I obtain permission to edit the wiki?

Thank you very much for you help!

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Alexander W. Winkler
Robotic Systems Lab, ETH Zürich
http://www.awinkler.me/