The check for continue_params&.key?(:to) in Projects::ImportsController
caused an exception in redirect_to if this key contained a nil value.

Since url_for won't add any params for an empty hash, we can just return
that in continue_params if params[:continue] isn't present, and simplify
the code in the controllers to check for the values we actually want to
use.

The `#reload` makes to load all objects into memory,
and the main purpose of `#reload` is to drop the association cache.

The `#reset` seems to solve exactly that case.

- concerns
- dashboard
- groups
- import

Signed-off-by: Rémy Coutable <remy@rymai.me>

Also adds Changelog entry

Clears the import related columns and code from the Project
model over to the ProjectImportState model

Enables frozen string for some vestigial files as
well as the following:

* app/controllers/projects/**/*.rb
* app/controllers/sherlock/**/*.rb
* app/controllers/snippets/**/*.rb
* app/controllers/users/**/*.rb

Partially addresses #47424.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Fixes
https://dev.gitlab.org/gitlab/gitlabhq/issues/2649
https://gitlab.com/gitlab-org/gitlab-ce/issues/13956

Fixes #13367.

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

While importing, don't redirect import actions to the project page, even if the repository exists

Make the following changes to deal with new behavior in Rails 4.1.2:

* Use nested resources to avoid slashes in arguments to path helpers.

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