[FEATURE REQUEST] FreeBSD Support

Hey, would love to use this on my TrueNAS Core server. I got the agent working by loading the Linux compatibility layer with `kldload linux64` and then running the agent, but it's not reporting uptime, CPU, or RAM.. only disk usage.

Here's a JSON response from the API on the TrueNAS server:
```json
{
"host_info_is_available":false,
"boot_time":-62135596800,
"hostname":"",
"platform":"",
"cpu":{
"load_is_available":false,
"load1_percent":0,
"load15_percent":0,
"temperature_is_available":false,
"temperature_c":0
},
"memory":{
"memory_is_available":true,
"total_mb":0,
"used_mb":0,
"used_percent":0,
"swap_is_available":true,
"swap_total_mb":17592186042368,
"swap_used_mb":0,
"swap_used_percent":0
},
"mountpoints":[
{
"path":"/mnt/tank1/media",
"name":"Media",
"total_mb":1234,
"used_mb":123,
"used_percent":10
},
{
"path":"/",
"name":"Root",
"total_mb":1234,
"used_mb":123,
"used_percent":10
}
]
}
```