Create a entry point class and enable customized php name

[xcompass]

In order to install other version of php than OS provided, we need to
customize the php package name, e.g. php54, php56

To install customized version of php, install third party repo first,
e.g. IUS, then using

class { 'php': php_name => 'php54' }

[thias]

This is a whole new can of worms right there :-)

I think my module needs some proper tests before I dare include changes like these. FWIW, I'm using mixtures of PHP 5.5 and 5.6 on RHEL6 and RHEL7 systems using my module, but what I do is have different repositories where php and php modules are all named without those prefixes.