Keep pit start and stop time for temperature profiles

[micah-prime]

Keep the start and stop time from the pit temperature profiles

This should go in the Site (sites) table. The data is structured as

# Depth (cm),Temperature (deg C),Time start/end
57.0,-20.3,10:32:00
50.0,-15.7,-9999
40.0,-12.1,-9999
30.0,-10.1,-9999
20.0,-8.7,-9999
10.0,-7.7,-9999
0.0,-5.3,10:39:00

In the raw files so some fancy parsing will need to happen. For now the table structure should just be able to have two new Time columns

[micah-prime]

After discussion with @jomey @aaarendt @micahjohnson150, we decided this should be captured in the JSON implementation of columns, so this will be a row-based variable