UTF-8 Migration tool

This is a tool to migrate a user or the whole system from whatever
legacy encoding it is currently using, to another UTF-8.  Migration
consists of multiple steps, some of which are system-wide, some which
are per-user:

System-wide:
- make sure the locale is generated
- change the language in pam's environment file
- change the GDM language (in /etc/default/gdm)

Per-user:
- change language in the user's DM session
  (the name in .dmrc is unqualified (nb_NO, nb_NO.UTF-8)
- convert file names

