[RFC] Use composer.json for styles and track phpBB version

[naderman]

My understanding of the current situation is:

1. Any style or modification can break at the next minor version.
2. Support team only supports the latest version.

Until these policies are changed specifying a single compatible version seems at least sensible to me.

I guess that makes sense.

[Marc]

I like the idea, both JSON & the seperation of the style versions, although it shouldn't be a hard limit. Warning the user that the style is outdated should be enough.

[naderman]

I'll merge the change now anyway to resolve problems with the updater. I still think we should go the same route as with extensions, and make this the same composer.json format.

[naderman]

I created a ticket for composer.json format for styles: http://tracker.phpbb.com/browse/PHPBB3-10824