The reload handler for firewalld is added.

Firewalled is needed for CentOS7.
Some wordings in task names are revised.
The Lxr DB file is asserted to be world writable.

This change is needed to avoid the dependency on umask and ansible.
A missing package(flex-devel) is added to 020-install_pkgs.yml.

CentOS7 minimal install does not install flex-devel that is required to build glimpse.
The work-around for ansible/ansible-modules-core #174 is incorporated.

The issue only appears on ansible 1.7.2.
    https://github.com/ansible/ansible-modules-core/issues/174
CentOS7 is supported.

CentOS6 specific parts are separated and included only when the target OS matches.  Also CentOS7 specific parts are added.