Add ability to disable projects (#97)

Conflicts:
	pootle/apps/pootle_project/models.py
	pootle/core/decorators.py
TranslationProject: added convenience `disabled()` manager method
translationproject: Add the ability to disable a translation project

Cherry-Picked-From: a6b5dd9db6e6495444730d4e33b354315e86e967
Disabled translation projects aren't to be updated

No log error messages while update_stores after whole directory
of translation project was removed

Cherry-Picked-From: 1ad4f599abe8c870c3793bc7facd95fed031aeb4
Tests: added Arabic language fixture
Tests: allow passing options when creating projects
Tests: added disabled tutorial project
Tests: added disabled TP
Tests: check `get_path_obj()` behavior
Tests: allow having stores with the same name
Partial pick: Arbitrary path support for checks' and overview stats

Pick note: This is a missing bit from the first pick.

Conflicts:
	pootle/apps/pootle_store/views.py
	pootle/apps/pootle_translationproject/urls.py
	pootle/apps/pootle_translationproject/views.py
	pootle/static/js/stats.js
	pootle/templates/editor/_scripts.html
	pootle/templates/translation_projects/overview.html
Followup: Retrieve this from settings

We already picked the commit that did this change, so no idea why it is gone.
New overview page for languages

Pick notes: Had to adjust the changes because we already picked later changes
    and other changes were not necessary.

Conflicts:
	pootle/apps/pootle_language/models.py
	pootle/apps/pootle_language/views.py
	pootle/apps/pootle_misc/browser.py
Partial pick: Clarify the difference between context and resource objects

Pick notes: This is picking the missing bit that we left behind in the first
    picking.

Conflicts:
	docs/developers/glossary.rst
	pootle/apps/pootle_store/views.py
New overview page for projects

Pick notes: Had to adjust the changes because our code was different. In this
    commit we lose tags in project listing.

Conflicts:
	pootle/apps/pootle_misc/browser.py
	pootle/apps/pootle_project/models.py
	pootle/apps/pootle_project/views.py
Partial pick: Simplified item generation

Pick notes: The rest of the changes in the original commit were already
    picked in the past.

Conflicts:
	pootle/apps/pootle_misc/browser.py
Restore project listing page without any bells & whistles

Pick notes: Had to do some adjustments because of code divergence.

Conflicts:
	pootle/apps/pootle_misc/browser.py
	pootle/apps/pootle_project/views.py
Redirect to user preferred language page from the home page

If there are no matching languages, the project listing page is displayed.

(The templates haven't been removed since the home page will be reworked
sooner than later)

Pick notes: Just solved the conflicts raised because of code divergence. Now
    the code is exactly the same.

Conflicts:
	pootle/apps/pootle_app/views/index/index.py
Removed unused stuff
Cleanup: removed unused table fields

Pick note: Minor conflicts because of the priority column for goals we have.

Conflicts:
	pootle/templates/browser/_table.html