Add future-proofing fields to stimConfig files

[raacampbell]

Each stimulus line should have the following:

• Attributes -- to store things like laser power at that position. Perhaps also parameters of a grid of points.
• Class -- So the user can in the future list optionally what this is. e.g. A control location or otherwise. For not it can be "stimulate"
• Type -- Right now the strings bilateral point or unilateral point

[raacampbell]

Done with bells on-- 84f83b89b317bfa000c49d5b527806a13b9fc71f