JSCS: fixes for missing errors.
Removed JSCS comments surpressing errors which are not thrown in the latest JSCS version.
Updated .jscsrc according to https://github.com/ckeditor/ckeditor-boilerplate/issues/2.
JSCS fixes after recent .jscsrc update.
Merge branch 'master' into major

Conflicts:
	core/editable.js
	tests/core/tools.js
	tests/plugins/forms/textarea.js
Tests: New tests for HTML and text insertion into not focused editor.
Editor must be focused before retrieving range and before transforming text to HTML what requires context.
Merge branch 't/12726' into major
Introduce uploadimage plugin.
Print drop files.
Added CKFinder to dev sample.
Added test php receiver.
Upload dropped file.
Create image from uploaded file.
Introduced data-cke-special-image.
Cache data.
Introduced uploadimage widget.
Added scope. Use strict.
Upload src data instead of file.
Introduce data-cke-image-to-upload.