puppet nftables

Migrate from deprecated mocha

Add nftables.version to structured fact.

```
FACTERLIB=. facter -p nftables {
tables => [
"bridge-filter",
"bridge-nat",
"inet-firewalld",
"ip-firewalld",
"ip6-firewalld"
],
version => "0.9.3"
}
```

New parameter noflush_tables to selectivly skip flush

Introduces a new structured fact nftables

```yaml
nftables:
tables:
- inet-filter
- ip-nat
- ip6-nat
- inet-f2b-table
```

By default the nft script will continue to contain `nft flush ruleset`...