Refactor code

[DylanVanAssche]

1. What happens:

   • Duplicate and complex code in several places

2. What was expected:

   • Use Singleton design pattern where possible (API, parsers, ...)
   • Move parsers to separate classes, use a superclass to combine the shared stuff
   • Photo and GIF are the same, use an abstract Image class
   • ...

3. How to reproduce:

   1. N/A

4. Environment:

   • N/A