Partially addresses #47424.

Closes #35658

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

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

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

Main idea is to keep left sidebar static so user is not confused by
changing context. Instead we put changing navigation with changing
content in one main block

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

* projects from explore page are available from dashboard
* use dashboard sidebar for both logged in and not users
* move explroe projects under projects tab
* move explore groups under groups tab
* move public snippets under snippets tab

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

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

Addresses #2278.

Make the following changes to deal with new behavior in Rails 4.1.2:

* Use nested resources to avoid slashes in arguments to path helpers.

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

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

Be default it sorts by name now
Respect filters like scope, label, visibility when do sort or another
filter

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

Also remove now-unused tab_class helper