* Improve the index keyword checker function
* Implement a more compact indented JSON encoder
* Remove timestamp from reference, novel and note indices
* Remove empty entries in reference index
* Merge novel and note indices into a single file index
* Subclass ConfigParser
* Remove redundant variables and update tests
* Update file description
* Move NWConfigParser class to common.py
* Improve coverage of config class
* Use NWConfigParser also in themes.py
* Update config class file header
* Fix comment
* Update the usage of ConfigParser to recommended practice and extend tests
* Improve logging for info level a bit