- Rename `Etcher.Utils.Dropzone` to `Etcher.OS.Dropzone`
- Rename `Etcher.Utils.OpenExternal` to `Etcher.OS.OpenExternal`
- Rename `Etcher.Utils.WindowProgress` to `Etcher.OS.WindowProgress`
- Rename `Etcher.notification` to `Etcher.OS.Notification`
- Rename `Etcher.notifier` to `Etcher.Utils.Notifier`
- Rename `Etcher.path` to `Etcher.Utils.Path`
Signed-off-by: Juan Cruz Viotti <jviottidc@gmail.com>