(CFACT-120) Add support for zfs facts for solaris

This patch adds support for zfs and zpool facts for solaris. There are two main versions of zfs out in the wild, the first is by Oracle, which follows a linear numbering scheme for its version, and the other is by OpenZFS which follows a tag scheme for version. Only solaris implementation is provided with this patch.

Unfortunately, there is no public API for programmatic access. Hence we are using the commands provided for fetching the facts.
@peterhuene How does this fit into your refactoring? In other places we haven't done overloading, we've simply defined the method separately for each platform where we use it.