Rename 'newhost.yml' playbook to 'bootstrap.yml'

Playbook syntax is also cleaned up and comments have better
explanation what is going on. Fixes #84.
Remove 'changed' from a task name

This can interfere while searching for changed tasks in the Ansible
output.
Remove 'playbooks/secret.yml'

This playbook is not needed anymore. Fixes #82.
Remove 'githost' role

This role has been superseded by 'gitlab' role. Fixes #82.
Condense separate application playbooks together

Separate application playbooks are now put together in
playbooks/applications.yml. playbooks/local_nat.yml playbook is removed
because it's no longer useful, other roles can replace it. Fixes #85.
Symlink /var/lib/vz to /vz on OpenVZ hosts

/vz symlink is required for correct operation of vzmigrate script.
Update CHANGELOG.md
Merge pull request #124 from drybjed/bugfixes

Various bugfixes