Load demo files

Instead of inserting your own data to the five setting boxes in the graphical user interface (GUI) one can load demo files of certain cases that are included in the CAT.

The different cases are:

Dissolution

Nucleation

Dilution

Size dependent growth

• [Dissolution](https://github.com/SPLIfA/CAT/wiki/Dissolution)
• Nucleation
• Dilution
• Size dependent growth