Moved utils to ckeditor5-dev-utils package

[maxbarnas]

Resolves: #252

WARNING This PR can be closed only after closing those PRs: https://github.com/ckeditor/ckeditor5-dev-utils/pull/2 and https://github.com/ckeditor/ckeditor5-dev-task-lint/pull/2

I updated modules depending on utils, added ckeditor5-dev-utils to
package.json and fixed build task to reflect needed changes in
ckeditor5-dev-utils package.

[Reinmar]

WARNING This PR can be closed only after closing those PRs: ckeditor/ckeditor5-dev-utils#2 and ckeditor/ckeditor5-dev-task-lint#2

Why do we have to close ckeditor/ckeditor5-dev-task-lint#2 before this PR? This PR is only about dev utils, so what has linting to do with it?

[maxbarnas]

It is because ckeditor5-dev-utils requires ckeditor5-dev-task-lint.

[Reinmar]

Ah, makes sense :).

[Reinmar]

(t/252 7f9eb46 ?1) p@m /www/ckeditor5/ckeditor5> gulp relink
(node:36332) fs: re-evaluating native module sources is not supported. If you are using the graceful-fs module, please update it to a more recent version.
module.js:440
    throw err;
    ^

Error: Cannot find module 'ckeditor5-dev-utils'
    at Function.Module._resolveFilename (module.js:438:15)
    at Function.Module._load (module.js:386:25)
    at Module.require (module.js:466:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/www/ckeditor5/ckeditor5/dev/tasks/build/tasks.js:17:26)
    at Module._compile (module.js:541:32)
    at Object.Module._extensions..js (module.js:550:10)
    at Module.load (module.js:456:32)
    at tryModuleLoad (module.js:415:12)
    at Function.Module._load (module.js:407:3)
(t/252 7f9eb46 ?1) p@m /www/ckeditor5/ckeditor5> ls node_modules/ | grep ckeditor5-dev-utils
ckeditor5-dev-utils
(t/252 7f9eb46 ?1) p@m /www/ckeditor5/ckeditor5> ls node_modules/ckeditor5-dev-utils/
CHANGES.md  CONTRIBUTING.md LICENSE.md  README.md   dev     gulpfile.js package.json    tests

[Reinmar]

OK, I should close https://github.com/ckeditor/ckeditor5-dev-utils/pull/2 first.

[Reinmar]

PRs in dev-utils and dev-lint are closed, so this PR can now be reviewed. First thing that should be done is running npm-check to remove unnecessary deps.

[szymonkups]

Package is located under devDependencies and it feels like a natural way to use such dev-utils package. But this way gulp init task will not put this package in development mode (it only takes dependencies from package.json). Is this intentional? This is utilities package but it is still developed by us, so this might be helpful. Maybe we need some option for gulp init task to also scan devDependencies?

[Reinmar]

This was intentional. The linting package will be required by all other packages anyway and using links everywhere makes no sense. So I think we should use a normal workflow here with releases and publishing. I even wrote in #215 (comment) that we need to update package.json after we finish refactoring to use versioned packages.