db_config_dialog.py: add_row():modify to accept nextline in description, return text for next field checking, set placeholdertext as hint for ValueColors; check changes before clicking on 'CLOSE'

adjust condition to correct behavior once the key of row is in data_list; report error when calling get_row_inputs() to report pattern error from param_dialog; adjust messages to make them clearer

Shorten all lines to 80 characters.

Remove commented code in calendar_dialog.py, channel_prefer_dialog.py,
mainwindow.py, time_power_squareddialog.py, and db_gui_superclass.py.

Rename channeldialog.py, channelpreferdialog.py, dataTypedialog.py,
dbgui_superclass.py, paramdialog.py, and plottypedialog.py to use
snake_case
Rename variables and functions in above files to use snake_case