BREAKING-CHANGE: Deprecate ordering by file-prefix ##-

[JosefBredereck]

Closes #1028
Closes #1176

Summary of changes:

Remove the ability to sort files and folders by the ##- prefix. Since that approach could become unhandy when you want to reorder your patterns.

(Reopening to split changes in code and starter kit file changes)

[aleksip]

Curious about a few things related to this PR:

• Does this also add the ability to specify the order in front matter?
• Will there be a transition period during which both methods are supported, so everything would be ordered based on possible file prefix first, and then based on possible front matter?
• Is there any estimate for when this will be in a release?

[JosefBredereck]

* Does this also add the ability to specify the order in front matter?

yes

* Will there be a transition period during which both methods are supported, so everything would be ordered based on possible file prefix first, and then based on possible front matter?

yes, there will be a transition phase

* Is there any estimate for when this will be in a release?

maybe at the end of september

[aleksip]

Awesome, thanks!

[JosefBredereck]

See my comments on #1237 for further information on testing.

[coveralls]

Coverage decreased (-0.2%) to 76.201% when pulling a75f06e on deprecate-ordering-by-file-prefix into 030a992 on dev.