Change type hint of parameter gaps and return value to list of tuples
containing two floats
from list of lists containing two floats. Fix problem where type
hinting does not support lists with defined structure.

Change type hint and documentation for parameter gapMin in getGaps from
int to float. This reflects its usage in plotting_widget.add_gap_bar.

Reorganize view

See merge request !32

Fix bug where some MSeed data sets have only one day of waveform data plotted

See merge request !34

Fix bug where some MSeed data sets have only one day of waveform data
plotted

Add tests and refactor trim_downsample_WFChan

See merge request !33

Rename downsample_waveform_chan to downsample_waveform_data

Move responsibility of writing to the waveform channel data dictionry
from downsample_waveform_chan to trim_downsample_WFChan.

Make downsample_waveform_chan return the downsampled list of times and
data instead of saving this information to the waveform channel data
dictionary. This makes the function comply with SRP.

Make trim_waveform_data uses local variables for the start and end
index of the trimmed trace list inside of the original trace list.
Currently, these indices are saved to the data dictionary and never
used again.

Make loadData uses factory pattern instead of instantiating data object directly

See merge request !30

Add tests for processing.py

See merge request !17

Add tests for functions in plottingData.py

See merge request !19

Add tests for functions in util.py

See merge request !22

Change detectDataType to return only data type

See merge request !26

PEP8 convention and docstrings for view/

See merge request !29