Fixed multi-homing feature and related bugs. (#2222)

[sio4]

This will fix #2222.

In brief,

• added structure Home as an interim solution (hope to be reshaped as Group structure in v1)
• adapted to the new structure
• fixed bugs related to this feature and pre-existing small ambiguous things (related to routes and middleware handling)
• renamed the function from Host() to VirtualHost() to make the name clear, and avoid conflicting with App.Options.Host.
• added clarified function descriptions for involved functions.

More details (including the details of fixed bugs or symptoms) will be added on issue #2222 to consolidate the information/history.

fixes #2222

[sio4]

oops? why CI is not running?

[dmuriel]

Hey @sio4, just wanted to thank you. I appreciate the work you did in this PR.

[paganotoni]

This looks good to me @sio4. I'm not sure how to run the tests against these (We're in github limbo). I wonder if you could send this to a branch within the gobuffalo/gobuffalo repo to see if that triggers the changes. Appreciate this @sio4!

[paganotoni]

Merging this. We can test it in development and release depending on how it behaves.

[sio4]

Thanks! I lately found your comment. :-)