Add dependency for the kernel version

[fumantsu]

Hi,

I don't know if it is possible to be added to this plugin or to the backport kernels (especially for OMV3). Kernels 4.7+ are not compatible with zfs 0.6.5.7 so when was available this kernel in the backports it was breaking the zfs and of course the plugin.
The support for kernels 4.7 (I guess also 4.8 based on this openzfs/zfs#5025) has been added to 0.6.5.8 but I'm wondering if there is a way since plugin is coming together with the new zfs versions to put a dependecy control.

[luxflow]

http://forum.openmediavault.org/index.php/Thread/7633-HOWTO-Instal-ZFS-Plugin-use-ZFS-on-OMV/?postID=126527#post126527
from omv-zfs version 3.0.4, 4.7 kernel is already supported
checkout this http://forum.openmediavault.org/index.php/Thread/7633-HOWTO-Instal-ZFS-Plugin-use-ZFS-on-OMV/?postID=126527#post126527