Fully implemented --end-of-week/-e switch ...

(was --week-offset/-w)

Added initial code for --week-offset CLI switch

Preliminary code to refactor CLI error messages

Reimplemented text output using Jinja2 templates

Initialisation of ignored CLI args moved to cli.py

Added basic plain text output

Fixed incorrect raising of PaperError

Added calendar initialisation via configuration

Renamed week() to make_week()

Major revamp of configuration handling ...

• Moved configuration file loading into Configuration class.
• Added config getter methods to Configuration.
• Updated and extended custom exception types.
• Restructured error handling.
• Factored out app name.

Fixed broken “offsets” for INFO202/S2

Deleted obsolete comment

Converted load_config() into Configuration class

Removed reference to PROG constant

Moved load_config() into config.py

Added configuration defaults ...

The app nows looks for configuration in ~/.config if no configuration
file is explicitly specified. If the default configuration isn’t found,
a default configuration file is copied into ~/.config.

Refactored program name

Renamed module