Adapt structure for #425

This is a proposition of structure modification for #425.
Just a few css tweaks at start, some changes after talking with @elemoine.

Multiples changes:
 - As there’s interaction with featuretree’s toggler, make it part of the partial 
 - remove controller that are only settings configuration uri, and move it to `featureTreeOptions` in MainController
 - scope css with with attribute selector of the directive (`[ga-featuretree]` here)
 - for object writing to MainController scope (such as importkml link), write into a globals property, to avoid an intermediate controller to break things

All these points would make sense to be applied in other components, imho.

Thanks for any review/opinions.

(as a side note, I wasn’t able to have data features after rebasing this, have you remove some testing stuff?)