closes #7076

* Adds a new metadata helper and methods to PostPresenter to have metas on post pages.

* Adds tests to post controller to check correctness of metas

* Add methods to PersonPresenter to have metas on profile pages

* Correct meta data helper test

* Update PersonPresenter, add test to PeopleController

* Creates TagPresenter. Display tag metas on tag index page

* Updata meta data helper spec

* Not displaying bio as the description meta on profile page for now. Privacy concerns to be cleared.

* Set meta info as hashes in presenters

* Move original hardcoded metas info to config/defaults.yml

* metas_tags include by default the general metas, update views

* Update code style, clean views

* Renames TagPresenter StreamTagPresenter, updates TagController spec

* Add a default_metas entry to diaspora.yml.example

* Align metas hash in presenters, refactor meta data helper

* Use bio as description meta if user has a public profile

* Rename StreamTagPresenter to TagStreamPresenter

closes #6398

closes #6243

This adds a new boolean field "public_details" to person model.
By default it is false and represents old behaviour. When it is
set to true, extended profile (bio,location,gender,birthday)
get available to people who didn't log into diaspora and to
people you don't share with (i.e. it is made public).

In UI, a bootstrap-switch added on the profile-edit page in order to
change the setting.

This also changes wording from public/private profile to basic/extended.
The latter could be public and limited.

Add specs to check mass-assignment gotchas in PhotosController.

  *people_controller#show
  *photos_controller#index
  *views/people/show both html and mobile