Close issue #19

[nomad-vagabond]

resolve #19. Clicking on Sun button preserves lock on the selected asteroid and doesn't remove its orbit. Add 'Reset' button to deselect asteroid and reset view (can also be helpful to restore view from weird camera angles and scales). Earth selection behaviour is intentionally left unchanged as asteroid tracking can be a bit complicated from the Earth-locked view.

[typpo]

Thanks Vadym for this excellent change :+1:

Could you help me understand the difference between clearLock and dropLock in the code?

[nomad-vagabond]

dropLock clears selection even if locked_object == null, while original method clearLock skip this action due to this line of code at the top: if (!locked_object) return. I implemented dropLock in order to force clearing selection from resetView method, which emulates absence of lock through declaration locked_object = null at the top. This declaration is needed to reset camera. A bit confusing - I know, but this is how I made it :) Please do not merge yet for I've just found a little bug in my ResetView method. I hope I'll fix it next week.

[nomad-vagabond]

Done!