change dates to times

content/GA_1_3/data/gnss_observations.csv

-,dates,observations[m]
+,times,observations[m]
 0,2017-01-01,-0.013980633493923006
 1,2017-01-02,0.010392229436626857
 2,2017-01-03,-0.01709087092486749

content/GA_1_3/data/groundwater_levels.csv

-,dates,observations[mm]
+,times,observations[mm]
 0,2017-01-01,-109.698
 1,2017-02-01,-102.044
 2,2017-03-01,-127.198

content/GA_1_3/data/insar_observations.csv

-,dates,observations[m]
+,times,observations[m]
 0,2017-01-01,-0.0037915269917409627
 1,2017-01-13,-0.005998562574055986
 2,2017-01-25,-0.011402835952374462