Make mixed-use more flexible

[shyamamrith]

Main issue:

• Currently the uses are fixed, since each requires their own thermostat objects which have been pre-defined in the base idf. It would be good to allow users to add as many uses as they need. Could consider getting Simstock to add in the required thermostat objects according to which uses are specified.
• Would need to add this functionality to setup_basic_settings()
• Give attention to mixed_use() in simstocktwo.py as well
• Need to add helpful warnings, e.g. if a use is specified but the corresponding objects are not included

Use-specific objects currently in base idf:

• ZoneControl:Thermostat
• ThermostatSetpoint:DualSetpoint

Default to 'Dwell':

• Assuming "Dwell" when the use columns are not present is currently hard-coded into simstocktwo.py. Would be better to generate the use columns in the main plugin process which simstocktwo.py passively reads without inferring anything itself.
• If the use columns are present, simstocktwo.py raises an error if one of the polygons does not have a specified use. In the current form, this is strange since the plugin is supposed to assume "Dwell" if use is unspecified. However, if the previous point is tackled, then this behaviour can be retained.