Added new option for always on location, regardless of clicks

Hello, I find the 'triple click' behaviour of the locate button a bit unnatural. I would prefer to:
1. Click once to follow/set the view and watch
2. Stop following on drag, but keep watching. 
3. Clicking again just relocates and follows (rather than switches off geolocation). 

For this I've added an `alwaysOn` option and negated the whole stopLocate behaviour on click, if it's true.