Add support for VTG forecasts

[maximecarre1]

The IWLS team is starting tests to integrate VTG stations forecasts to the database; support for the new data source (wlf-vtg) will need to be added to IwlsApiConnectorWaterLevels()

[maximecarre1]

S104GeneratorDCF8() also needs to be updated to support VTGs.

[glmcr]

Which TG is used to test the VTG forecasts exactly? I now see a choice of wlf-vtg for Sept-Iles on the IWLS dev server but no data seems available for now.

[maximecarre1]

I'm not sure of the current coverage; data is only in neptune-dev for now.

[glmcr]

Since the VTG data we will use will come from the IWLS RTDB itself then it is a forecast like another one and we will just have to set the related metadata name (methodWaterLevel*) and the time increment (1 hour).

[maximecarre1]

Past hindcasts may also be stored in the same database entry for wlf-vtg, we will have to decide if we keep them together with the forecasts in S-104 files or split them by water level data type. (different values for dataDynamicity)

[glmcr]

I would say let`s keep it all as forecasts for now even if it is in the past compared to the time of the S-104 DCF8 files production. The other option would be to only take the timestamps of the future for the S-104 DCF8 data (this would also apply to any forecast data). We will see later if we really need to separate the hindcasts from the forecasts. Note also that it is likely that we will propose a nowcast data type for the next S-100 specs