Server Compatibility with Apache 2.4.x

Apache handles configuration files different as of version 2.4.x
Before it included all files in the `conf.d` subdirectory, now it uses the directories `conf-available` and `conf-enabled` similar to `site-available` and `site-enabled`. This Pull Request includes code to distinguish the different apache versions and to act accordingly.
Additionally the configuration files need slight adaptions. Namely general access is not stated through:
```
Order allow,deny
Allow from all
```
anymore, but needs to be configured like:
```
Require all granted
```

This distinction is done as well. Though I do not really like the approach, maybe you have a better idea?