Use past tense in metric names

@jh-bate @kentquirk A small tweak in metric naming, if you guys are ok with it, I think it would be nice to be consistent and use the "start with verb in past tense"-convention that I used in Blip to name these events?

So the list in Clamshell now looks like:

- Logged In
- Logged Out
- Opened Menu
- Closed Menu
- Changed Selected User
- Viewed Note Thread
- Added Note
- Added Comment