Machine Group Policy for Stained Glass OS.

Drop .reg files here (root-owned). At boot, sg-services-start imports them into
the machine registry as the SYSTEM account, so they land in the
administrator-owned HKLM policy branches and bind every user -- a user cannot
override them (wine-sg 0024/0025).

Policies go under:
  HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\...   (shell/Explorer)
  HKLM\Software\Policies\...                                    (application/OS)

Example -- forbid shutdown and sign-out from the shell (see 10-example.reg,
shipped disabled as .reg.example):

  Windows Registry Editor Version 5.00

  [HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
  "NoClose"=dword:00000001
  "StartMenuLogOff"=dword:00000001
