[mavo] Some fixes (#799)
[mavo] Some fixes (#799)

* Even though when [] is coerced to a number it becomes 0, let's be explicit here

* Fix protocol (switch to https)

* We shouldn't load remote data immediately. We should take conflict policy into account first

* Let authors use the [mv-progress= "Uploading"] selector in their stylesheets if they need it (and for the sake of consistency with other parts of the codebase)
mavoweb/mavo