Extend warning for not readable configuration file. unify mains accordingly.

• fixes indention in cpu mains
• removes unused bool return value from ConfigurationFile::load()
• uses helper function loadConfig in cpu apps
• exchange UBException in ConfigurationFile::load() with std::invalid_argument
• in mains removes not needed catches like: bad_alloc() (will be caught with std::exception anyway), (...) - wildcard is never used and spdlog exception will also be caught by std::exception
• exchanged critical error with warning in mains for caught exceptions
• extends error message in ConfigurationFile::load() with link to documentation

Closes #188 (closed). Follow-Up: #190 (closed)