Tiny improvements for template details

[blindzero]

ping.ini icmp.ini hostalive.ini Changed yUnitSystem from "none" to "msec" to be more accurate disk.ini swap.ini Changed legend from "Used" to "Free" as the default perfdata output of Icinga plugins delivered are based on this. Otherwise the graphs are "wrong way around". The screenshot of changed behaviour should explain it as a living example. If the filled area would be "Used" the state would be critical (nearly all Swap used), but it isn't as the filled area is still available.

P.S.: This is my first other project pull request, so please be gentle ;)