Correct `#user .logged-in` ids and icons

* The env admin link and the user pannel had the same controlpanel id.
* The user icon is now recovered.
* The #manage-enterprises icons was croped.

Closes ActionItem2817
finishing action item 2722
Finishing unit test action item 2722
Fixes the layout of nested comments on the wall

  - Makes the hierachy clearer with padding.
  - Removes a white border that was giving the impression of broken
  layout.

(ActionItem2726)
(ActionItem2725)
Adds user icon for null avatar on user menu

That commit makes gravatar helper to work on this context.
uploaded-file: don't display private images thumbnails and private images on slideshow

AI2824
Merge commit 'refs/merge-requests/376' of git://gitorious.org/noosfero/noosfero into merge-requests/376

Conflicts:
	db/schema.rb
Merge commit 'refs/merge-requests/392' of git://gitorious.org/noosfero/noosfero into merge-requests/392
erge commit 'refs/merge-requests/390' of git://gitorious.org/noosfero/noosfero into merge-requests/390
Merge commit 'refs/merge-requests/387' of git://gitorious.org/noosfero/noosfero into merge-requests/387

Conflicts:
	app/helpers/application_helper.rb
	public/designs/themes/base/style.css
Merge commit 'refs/merge-requests/425' of git://gitorious.org/noosfero/noosfero into merge-requests/425
Better support for plugins migrations
Load init.rb after paths are loaded
Support to skip validation with a session data
Merge remote-tracking branch 'noosfero/stable' into escambo
OAuth client and provider plugin
Merge branch 'oauth' of git://github.com/coletivoEITA/noosfero-ecosol into escambo

Conflicts:
	lib/tasks/plugins.rake