EAGERx as dependency instead of submodule. (#228)

* EAGERx as dependeny instead of submodule. Docs and demos updated accordingly

* Fix typo

* Minor fixes

* Update test_pep8.py

* Loosen pyqglet requirements to solve dependency issue

* Loosen pyglet requitement to solve dependency issue

* Update dependencies

* Update dependencies

* Update EAGERx

* Fix typo

* Add rendering toggle to eagerx demos

Co-authored-by: Jelle Luijkx <j.d.luijkx@tudelft.nl>
Co-authored-by: ad-daniel <44834743+ad-daniel@users.noreply.github.com>