Added public groups area to enhance searching and exploring of projects

fixed whitespaces and quotes

fixed whitespaces

fixed devise.html.haml

fixed method parenthesis in app/models/group.rb

removed links from header

removed links from devise.html

added tests
Merge branch 'public-groups' of https://github.com/innogames/gitlabhq into 7-2-dev
Explore area

Create one place for exploring GitLab instance projects and groups for
both signed in and anonymous users

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Refactor explore area

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Refactor explore area tests. Replaced old links

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Remove duplicate test

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch '7-2-dev' into 'master'

Explore area

Fixes #1426

See merge request !987