fixes #3752 - move data population from migrations into seed script

This looks more severe than it is I think.

1. all data removed from migrations, moved into seeds.rb
2. templates under app/views/unattended/ all rearranged to fit the community-templates layout.  All moved into community-templates and refreshed from there.
3. as such, I removed the unattended controller feature of hardocded names (like "pxe_kickstart_config") and so it now only works with template kinds.  The tests + fixtures needed a few updates.  I'll update the release notes.
4. the spec file runs the db:seed on every installation/upgrade.  Installer PR's in, will do a deb one shortly.

I think this is more reliable than the DB migrations.  I was beginning to implement [improved admin account initialisation](http://projects.theforeman.org/issues/3272) and the use of DB migrations was hampering me, as they have to support both upgrades and initial installations - they're quite fragile as a result.