Update csv headers

Add column descriptions for each Source csv.
Remove quotes around header text.
Remove comma in event data csv header,
comma still present in datetime.
Change datetime formats for data downloads

Prevents comma's in csv headers.
Perhaps making Excel more likely to recognize tabs as the delimiter.
Reword line in coincidence download, like for other data.
Add station numbers and dates to source csv

Add station number and/or date to source csv files where applicable.
Removed comma's that I accidentally let slip in..
Small updates to docs
Merge branch 'detector_positions' of https://github.com/HiSPARC/publicdb into detector_positions