* 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