Package managers integration

[Piotrek Koszuliński]

There are plenty package managers out there, but let's focus first on two of them:

• Bower (JS)
• Composer (PHP)

Steps:

• Make all necessary steps to make CKEditor easily installable with those PMes. The package that should be installed by default is stable/standard (which equals master) from ​https://github.com/ckeditor/ckeditor-releases. If PM allows to have alternative, we can also make other (basic and full) presets installable.
• The above will perhaps require: #10882. We already tagged CKEditor 4.3 as 4.3.0. To close #10882 we should also add missing tags for historic releases (4.3.0-beta, 4.2.0, 4.1.0, 4.1.0-rc, etc). Additionally, to conform ckeditor-releases with SemVer we may need to create tags without "/standard|basic|full" suffix - e.g. 4.3.0 === 4.3.0/standard.
• Readmes in ckeditor-dev and ckeditor-releases have to be updated. The ckeditor-dev's mentions the 4.0 tag and ckeditor-releases has to contain information about installing CKEditor with Bower and Composer.
• Installing through package managers has to be mentioned in our guides. Please contact Ania to choose the best place.
• The PM integration should be mentioned in release blog post.