Dump for all windows / per view

Fixes #120 - JSON dump of any view

Replaced `DumpCommand` with `DumpCommandRoute`, allowing the following URIs

`/dump`  - dump (`keyWindow` for iOS, everything for Mac)
`/dump/allwindows` (dump everything)
`/dump/view/UID` (dump view with the given UID)
`/dump/views/UID` (dump view with the given UID and its subviews)