Project needs recompiling each time exercises are modified

[iK4tsu]

Currently, all exercises are added in source/info.d. Although they are read at compile time, it also means the project needs to compile to update any changes (addition or removal of an exercise, order swap, any data relative to their properties). Adding the exercises in an external file read at runtime would allow modifications to be made a lot easier. Using a toml or yaml format makes this possible, it's easy to parse, and maintains the nice readability.