Improving speed of the simulator core

Briefly, the simulator is too slow for many applications, and we (Marmaduke & Mathieu Golos) will begin working on ways to speed it up. Our work will be organized in the repo

https://github.com/the-virtual-brain/tvb-sym-gen

I wish to note this here so that it's tracked in JIRA. The due date of June 7th is a goal but not absolute.