Refactor upload and replace functionality

    Rename file and move CSS

    Fix typo

    Make dropzone a div

    Remove unnecessary file

    Change color of "upload existing one"

    Add missing changes

This reverts commit 6014019e.

Fix reading session_expire_delay when application settings are not yet created and migrations are not yet done

- Split up SnippetsController into separate dashboard and explore sections.
- Use consistent page titles, header titles and sidebars between dashboard and explore sections when signed in or not.

This is the quickest/dumbest/safest way I could think of to prevent
the instance variable reuse problems we have on dev.gitlab.org now.

Closes #2104

Closes #1751

Closes #1592

Closes https://github.com/gitlabhq/gitlabhq/issues/9399

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

Closes #2335

This reverts commit 5daf44b7, reversing
changes made to 2f706fbd.

This reverts commit 957e849f, reversing
changes made to 6b9dbe9f.
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

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

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

Closes #2116
Closes https://github.com/gitlabhq/gitlabhq/issues/9502