Revamp administration pages

Demo's current administration pages are not in line with other administration pages in Drupal. I suggest to do the following:

1. Rename the title for admin/structure/demo from "Demonstration site" into "Snapshots".
2. Make the first (default) local task "List", i.e. the current "Manage snapshots" form/page.
3. Move the currently first "Status" task to the end and rename it to "Settings".
4. Keep the "Reset" local task + confirmation form.
5. Remove the confirmation form for the "Create" (snapshot) form. Instead, add an optional confirmation to overwrite an existing snapshot. (the original reason to make it one)
6. Move the "Status" fieldset from Settings to the "List" (ex. Manage) form/page.
7. Remove the form submission redirect from the Reset form. When resetting, it's likely that you want to reset all over again (keeping the browser tab open).

Effectively:

• List: Status + List of snapshots (default local task)
• Create: Like now, just shortened. Add confirmation form for overwriting existing snapshot.
• Reset: Just shortened, but also remove redirect.
• Settings: Module settings, system_settings_form().