adding proper htaccess commands for Apache 2.4

Fixes #5757 

Generated content will look like this:
````
# Generated by ownCloud on 2013-11-08 09:32:48
# line below if for Apache 2.4 - please uncomment if you run Apache 2.4
# Require all denied

# line below if for Apache 2.2 - please remove it once you upgrade to Apache 2.4
deny from all

# section for Apache 2.2 and 2.4
IndexIgnore *