Standardize the way we check for and display form errors

- Some views had a "Close" button. We've removed this, because we don't
  want users accidentally hiding the validation errors and not knowing
  what needs to be fixed.
- Some views used `li`, some used `p`, some used `span`. We've
  standardized on `li`.
- Some views only showed the first error. We've standardized on showing
  all of them.
- Some views added an `#error_explanation` div, which we've made
  standard.

See merge request !3531

- Some views had a "Close" button. We've removed this, because we don't
  want users accidentally hiding the validation errors and not knowing
  what needs to be fixed.
- Some views used `li`, some used `p`, some used `span`. We've
  standardized on `li`.
- Some views only showed the first error. We've standardized on showing
  all of them.
- Some views added an `#error_explanation` div, which we've made
  standard.

Fix missing tooltip in project title

closes #14516 

![tooltip](/uploads/121cc3676f4f32044e158cf5f3df5be5/tooltip.gif)

See merge request !3351

Display nav controls on mobile

Set inputs inside .nav-controls to full-width on viewports below 600px

Fixes #13885

**Affected pages**


/dashboard/groups

/admin/builds

/dashboard/projects

/dashboard/issues

/dashboard/merge_requests

/dashboard/milestones

/dashboard/todos

/explore

/groups/{group-name}/issues

/groups/{group-name}

/groups/{group-name}/milestones

/{group-name}/{project-name}/builds

/{group-name}/{project-name}/forks

/{group-name}/{project-name}/issues

/{group-name}/{project-name}/labels

/{group-name}/{project-name}/merge_requests

/{group-name}/{project-name}/milestones

/{group-name}/{project-name}/wikis/home

/{group-name}/{project-name}/wikis/pages


Some Screenshots

**Groups**

![Screen_Shot_2016-03-15_at_2.22.23_PM](/uploads/b55348676693cc3ff67cddc4528f7f6c/Screen_Shot_2016-03-15_at_2.22.23_PM.png)


**Admin > Builds**

![admin-builds](/uploads/2e84119660f4895a1530883412c4b728/admin-builds.png)


**TODOs**

![todos](/uploads/84344c43011e22f902701038932d3eaa/todos.png)

**Dashboard > Projects**

![dashboards-projects](/uploads/f508d9107598038798aa10485d3d5cfe/dashboards-projects.png)


**Project Issues**

![issues](/uploads/d6c69a8f81ee07da95b2a3b99b81cf51/issues.png)


**Project Merge Requests**

![merge_requests](/uploads/b3c1a537f28931bd38077c36627a0d7a/merge_requests.png)


See merge request !3214