use https URLs for submodules

since that's what GitHub recommends these days
Merge remote-tracking branch 'origin/5.0.x'
Merge remote-tracking branch 'origin/master' into core

Conflicts:
	.gitmodules
Merge remote-tracking branch 'origin/core' into headless

Conflicts:
	.gitmodules
Merge remote-tracking branch 'origin/headless' into minimal

Conflicts:
	.gitmodules