Change command line api for role management

Deprecate the *-roles vagrant commands in favor of a `vagrant roles`
command with sub-commands. The legacy *-roles commands will still work
but they will no longer be listed in the default command list provided
by Vagrant.

  $ vagrant roles
  Usage: vagrant roles <command> [<args>]

  Available subcommands:
      disable  disables a mediawiki-vagrant role
      enable   enables a mediawiki-vagrant role
      list     lists available mediawiki-vagrant roles
      reset    disables all optional mediawiki-vagrant roles

  For help on any individual command run `vagrant roles COMMAND -h`

Change-Id: I56509c815b9ac4d09970f2e37a79ebe5c5c4577b