[TASK] Added composer.json for the TYPO3 CMS project

Added a composer.json file that contains
* name, description, keywords, homepage and license
* authors (core team and community)
* several support addresses
* requirements (php, php extensions and the composer typo3 installer)
* suggestions for php extensions
* branch alias for current development version (6.2)
* the packages, that are provided (system extensions)

Resolves: #55770
Releases: 6.2
Change-Id: Ibb94787ee12f9e580dedb1652c444f35e51d1aa9
Reviewed-on: https://review.typo3.org/27423
Reviewed-by: Fabien Udriot
Tested-by: Fabien Udriot
Reviewed-by: Thomas Maroschik
Tested-by: Thomas Maroschik