Related merge request text alignment

Fixed the alignment of the text 'When this merge request is accepted...' on issues page

![Screen_Shot_2016-05-23_at_14.59.48](/uploads/5d2f4be94108364a9d004169a6825a9e/Screen_Shot_2016-05-23_at_14.59.48.png)

See merge request !4251

Issuable filtering improvements

This improves the filtering of issues and merge requests by creating a single file that encapsulates all the filtering. Previously this was done with a file for issues and a file for merge requests.

Created the ability for the text search to be done alongside other filterables. Previously because this was outside the filterable form, this wasn't possible and would instead do either filter dropdown or text filter - not both. Fixes #4252 

Fixed issue with not being able to filter and sort issues without refreshing the page. Fixes #15269 

See merge request !3699

Fixed issue with GitLab import buttons having a spinner

![import](/uploads/db635f1d62affefca027d5fd4f545cd1/import.gif)

Closes #17232

See merge request !4276

Move tags to column in generic_commit_status

Part of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4249    

cc @ayufan 



See merge request !4277

Fix grammar and wording in text on various pages.

## What does this MR do?

Fixes various grammatical and/or wording issues I found while copyediting on the plane :)

## Why was this MR needed?

Incorrect grammar and weird/confusing wording makes the product look less polished and professional.

See merge request !4237

Increased zindex of layout nav

This fixes issues where group inputs would be above the dropdown in the nav

![Screen_Shot_2016-05-17_at_10.14.18](/uploads/08e4a43922051c28377ae6f34725ccc6/Screen_Shot_2016-05-17_at_10.14.18.png)

Closes #17524

See merge request !4176

Fixed issue with button color when no CI enabled

## What does this MR do?

Fixes an issue with the color of the merge button when no CI is setup.

## What are the relevant issue numbers?

Closes #17844

## Screenshots

![Screen_Shot_2016-05-25_at_09.58.44](/uploads/87aac74c5e2f8bfd2831e99c5915856d/Screen_Shot_2016-05-25_at_09.58.44.png)

See merge request !4287