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 ;)

[Al2Klimov]

Hello @blindzero and thank you for contributing!

Have you also tested the disk graph?

Best,
AK

[blindzero]

Hi @Al2Klimov
I think so ;)

You can see that the free is really free, compared to check output:
DISK OK - free space:C:\ 18460 MB (21%)
Best,
M.

[Al2Klimov]

Ran check_disk and check_swap on the command line. Swap seems to actually yield free space, but disk yields the used space.

@bobapple Does msec vs sec matter depending on whether your Graphite data is in s or ms?