vmctl: properly convert influx bools into integer representation
When using vmctl influx, the import would fail importing boolean fields
with:
```
failed to convert value "some".0 to float64: unexpected value type true
```
This converts `true` to `1` and `false` to `0`.
Fixes#1709
The `::tag` type is needed in cases when field and tag names are equal, which
results into unexpected results in InfluxQL. Setting the type explicitly helps
InfluxDB to understand which exact column we apply filter to.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1299
It is better developing vmctl tool in VictoriaMetrics repository, so it could be released
together with the rest of vmutils tools such as vmalert, vmagent, vmbackup, vmrestore and vmauth.
