Add last parameter to the physical_timeseries REST API endpoint

[dajtxx]

The start and end are not very friendly for charting, it would be nice to be able to say last=nx where

• n is an integer
• x is h hours, d days, m months, y years

So last=3h returns any messages from the last 3 hours, etc.

Perhaps a limit=n would be good too where n means the most recent n messages.

[kebab01]

I see that this issue was fixed on the 14th July with commit id: 787532deb0056525206fdabd9616911b44045e10