Support for flexible default middleware

[Ryanfsdf]

Introduced support for default middlewares and also the concept of "default dependencies". Default dependencies support glob patterns similar to the recent "flexible directories" feature.

[coveralls]

Coverage increased (+0.2%) to 68.519% when pulling c5b7d2c on flexible-default-middleware into a21d589 on master.

[Ryanfsdf]

@ChuntaoLu I know in the last pull request, you mentioned that JSON is no longer supported and we should remove the check for json files in general. However, edge-gateway still uses json files so I've kept the json file checks for compatibility.

[ChuntaoLu]

Is this PR supposed to replace #553?

[Ryanfsdf]

Is this PR supposed to replace #553?

Yes. Although a large portion of this pull request is the same as that pull request, I've had to rework quite a bit of the logic in this one to support glob patterns. I'll close the old pull request.

Hopefully this is the last pull request related to default middlewares (unless there's another big merge conflict, but I don't see any problems with any branches right now)

[ChuntaoLu]

Is this PR supposed to replace #553?

Yes. Although a large portion of this pull request is the same as that pull request, I've had to rework quite a bit of the logic in this one to support glob patterns. I'll close the old pull request.

Hopefully this is the last pull request related to default middlewares (unless there's another big merge conflict, but I don't see any problems with any branches right now)

New PRs makes it hard on review side because the progression/context in the old PR is lost. Ideally we should work on the old PR but I understand in this case because the merge conflict is annoying and hard to manage too.

[Ryanfsdf]

Is this PR supposed to replace #553?

Yes. Although a large portion of this pull request is the same as that pull request, I've had to rework quite a bit of the logic in this one to support glob patterns. I'll close the old pull request.
Hopefully this is the last pull request related to default middlewares (unless there's another big merge conflict, but I don't see any problems with any branches right now)

New PRs makes it hard on review side because the progression/context in the old PR is lost. Ideally we should work on the old PR but I understand in this case because the merge conflict is annoying and hard to manage too.

I'll keep note of that for future PRs. Thanks a lot for the review!