made setters, getters, and fixed spelling mistakes

This is a very small pull request but I thought it would be worthwhile to have on it's own for it's potential to break things for other people. If you use TGRSITransitions at all please read this! 
1. I have protected the members of TGRSITransitions, but made the TNucleus a friend class of the transitions. So this shouldn't change anything if you directly used the TNucleus. 
2. I then made setters and getters to the TGRSITransition members so please switch to those if you need to.
3. Finally the word uncertainty in TGRSITransition was spelt uncertainity and this drove me nuts trying to figure out why my compiler was grumpy, so I changed that to the proper spelling to avoid future headaches. However, this shouldn't be a problem for anyone because if it is, you would have had to change something at point 2. anyway. Sorry if this causes issues for anyones scripts, but I think this is the correct and safe way to do this.