Add rake task to install or upgrade gitlab-shell installation.
Add documentation for new rake task to install gitlab-shell.
Modify release dates for EE and CI

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'update-release-dates' into 'master'

Update release dates
Merge branch 'improve-gitlab-shell-installation' of https://github.com/pkgr/gitlabhq into pkgr-improve-gitlab-shell-installation

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

Conflicts:
	doc/install/installation.md
Fix install docs for gitlab-shell setup rake task

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix gitlab-shell setup rake task

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Merge branch 'pkgr-improve-gitlab-shell-installation'
Merge branch 'master' of dev.gitlab.org:gitlab/gitlabhq