Create last week table

[peterdudfield]

Detailed Description

Make a table that only stores forecast data for the the last week

Context

This can be read to speed up looking at 4 hour view

Possible Implementation

• add new table (copy of forecast_value) with migrations script
• make forecast save to that table as well
• update API to read that table when loading 4 hour forecast

[peterdudfield]

I have put these table on dev, need to update forecast and api to read from this table

[peterdudfield]

update the forcast and api