remove EE specific code
remove EE licence checks
move migration from EE to CE folder structure
move specs from EE to CE folder structure
remove EE specific flag specs

Updates the layout of the admin appearance settings to be consistent
with other settings pages across GitLab

Rename btn-new, btn-create and btn-save to btn-success
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See https://gitlab.com/gitlab-org/gitlab-ce/issues/47677 for more information

the initial reason for this change was that graphicsmagick does not
support writing to ico files. this fact lead to a chain of changes:

1. use png instead of ico (browser support is good enough)
2. render the overlays on the client using the canvas API. this way we
   only need to store the original favion and generate the overlay versions
   dynamically.
   this change also enables (next step) to simplify the handling of the
   stock favicons as well, as we don't need to generate all the versions
   upfront.

this ways we can keep the `lib/gitlab/ci/status/*` classes to return the
bare favicon name as it was before.

also the favicon uploader versions are now have the same names as the
stock favicons (+ `favicon_` prefix), which makes working with the
status names easier.

In the new navigation header, when a user uploads a custom header
logo GitLab will still show the 'GitLab' type logo. This is often
undesirable as the user may want to upload a logo with their own
name present. This change will toggle the GitLab type logo if a
custom header logo is present.

Adds rel="noopener noreferrer" to all links with target="_blank"

See merge request !2071

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

- 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.

The only major difference with the EE version is the change from a light and dark logo to only a header logo
The dark logo wasn't used anyway, so it seemed to make sense to me to rename the field to the actual function of it