add support for dot in header namespaces

[gvolpe]

This PR allows headers to be defined in the following form (fixes #47):

[gnome.desktop.interface]
cursor-theme='Yaru'

But it always replaces . with / to be consistent (especially with custom roots), resulting in the following output:

"gnome/desktop/interface" = {
  cursor-theme = "Yaru";
}

We need confirmation that programs using such settings via dconf have no issues with the change from . to /.

[Krutonium]

For the instances of it that I have, the programs that are affected don't seem to care either way

[gvolpe]

@Krutonium the question is, would your program still work correctly if the namespace changes . for / as in the example above? That the affected programs don't seem to care does not give me confidence 😄

"gnome/desktop/interface" = {
  cursor-theme = "Yaru";
}

The draft PR works fine if it's done this way but if we need to keep the ., it requires more work, mainly because of the custom roots functionality where you can pass --root /system/locale and it will then be appended to the parsed namespace.

[Krutonium]

As I said, swapping . to / seems to work just fine.

[gvolpe]

Ah that's what you meant with "they don't seem to care", ok, if that works it's good enough 👍🏽