Initial new versioning schema

* Removed "minimum-stability": "dev" from all composer schemas.
* Updated all Sylius bundles branch aliases to "1.0-dev" which means that bundle can be required via "1.0.*@dev" or  just "1.0.*" if you stability setting allows it. The 0.x.0 releases will still be supported until we hit 1.0 obviously.
* When I test all these changes, I plan to release v0.5.0 of main app and all bundles. Why jump to v0.5.0? Because v0.4.0 is the highest released version and we can overriding all the tags below v0.5.0 on other bundles.

As now all packages are developed inside this repo, they can't get broken on 1.0.*@dev, but you will still be able to lock on particular released version from 0.x.x tree.

Thoughts?