1) add functions in module hra_core.datetime_utils:
def __format_as_datetime__(_s_datetime)
    function used internally to convert string datetime into
    real datetime object

def convert_strings_to_datetimes(iterator, _format):
    function converts iterator of strings into datetime objects,
    example _format specification:
    '%H:%M:%S.%f' <=> "08:21:44.020"

def get_miliseconds_from_timedelta(tdelta)

2) add a function:
hra_math.utils.array_utils.get_datetimes_array_as_miliseconds_intervals(datetimes,
_format)
    which converts array of datetime strings into milisecond intervals,
    datatime items are parsed acccording to _format parameter;
    (assumption: it is assumed that datetimes are beginning of
intervals)
    an example:
    input array (could be any iterable, including numpy array):
    ["08:21:44.020", "08:21:44.870", "08:21:45.550",
                         "08:21:45.900", "08:21:46.333"]

    output array (numpy array):
    [850 <=> ("08:21:44.870" - "08:21:44.020"),
     680 <=> ("08:21:45.550" - "08:21:44.870"),
     350 <=> ("08:21:45.900" - "08:21:45.550"),
     433 <=> ("08:21:46.333" - "08:21:45.900")]

    important note:
    output array has a size less by one as compared to input array,
    there is no equivalent in the output array of the last item
    of the input array, because there is no end time for the last item

3) change in a method:
hra_math.model.data_vector_file_data_source.DataVectorFileDataSource.getDataVector(self)
        change time array expressed in datetime units
        into miliseconds periods; returned time array is less by
        one then time parameter array