Add type hint to controller code

See merge request !31

Add type hint to model code

See merge request !36

Fix bug where content of ASCII files are read twice.

See merge request !52

Fix bug where content of ASCII files are read twice.

# Conflicts:
#	sohstationviewer/controller/util.py
#	sohstationviewer/view/plotting/time_power_squared_dialog.py

Makes database code pep8 compliant

See merge request !20

Display and search on help documentation

See merge request !39

Move data loading to a separate thread

See merge request !46

Create mechanism to load data in a separate thread.

Implement ability to stop loading data.

Add documentation to note that loadData and
DataTypeModel.create_data_object are deprecated.

Implement deleting temp data folder on start

Closes #41

See merge request !48

SOH message dialog

See merge request !45

add logIdx to the downsample function

See merge request !38

Save current working directory to DB

See merge request !43

Print traceback error's info

See merge request !44

Shortcut, tooltip, pep8

See merge request !40

Showing info when click on a clickable data point

See merge request !37