Function get_nearest_time() behaves as expected now

A FilterAlgorith.py module function get_nearest_time() is supposed to return the nearest allowed time for a given filter "step". This worked fine with steps for second and minute data, whose allowed times are the tops of seconds and minutes. However, for hourly (and daily, and any "average" type step), things failed since the allowed times are the center of the interval (for example, for hourly data, which is the average of all minute samples from 00 to 59, the the allowed time is 29:30).

One consequence was that if a user specified an interval with a start and end time that did not encompass a given hour's allowed center time (e.g., start=AA:29:31, end=BB:29:29), the algorithm would still return a sample for time BB:29:30. More generally, requests for average type data would include an extra sample.

In this fixed version, if start=AA:29:31, and end=BB:29:29, nothing is returned, as intended (and as always worked for non-average type steps). Furthermoref start=AA:29:30, and end=BB:29:29, a sample for hour AA is generated; if start=AA:29:31, and end=BB:29:30, a sample for hour BB is generated, and if start=AA:29:30, and end=BB:29:30, samples for both AA and BB are generated, all as intended.

test/algorithm_test/FilterAlgorithm_test.py

@@ -313,7 +313,7 @@ def test_get_nearest__oneday_average():
     f = FilterAlgorithm(input_sample_period=60.0, output_sample_period=86400.0)
     step = f.get_filter_steps()[0]
     time = UTCDateTime("2020-08-20T01:00:00")
-    aligned = get_nearest_time(step=step, output_time=time)
+    aligned = get_nearest_time(step=step, output_time=time, left=False)
     # filter is average for day, should be first/last minute samples of 2020-08-20
     assert_equal(aligned["data_start"], UTCDateTime("2020-08-20T00:00:00"))
     assert_equal(aligned["time"], UTCDateTime("2020-08-20T11:59:30"))