Edit Width doesn't work for in-line _edit controls

Summary: If I create a control in my form, like MyProp._edit, the Edit Width, as well as the native editorSpan of the type, aren't respected.

I originally thought they were just plain broken, but the issue is much subtler and nastier. As discussed in the comments, the problem is that simply sticking an _edit inline like that means that it isn't in the Bootstrap grid, so even if we were generating the relevant col-md-n classes, they wouldn't work. So it isn't obvious how to fix this.

If we come up with a conceptual fix, it should probably be handled, instead of trying to change the _edit control's own HTML (which is tricky, because we use HtmlRenderer.renderPropertyInput() from multiple places), by wrapping the control in a span of the correct size, in EditorModule.applyToPropAndThing().