Added ability to set custom amount

[memeToasty]

Changelog:

• Changed from C to C++
• Added .vscode/-folder to .gitignore
• Corrected C-compilerflags in Makefile
• modified setcoins() method to accept one single integer now that gets "converted" to little endian
• Added menuentry to set custom amount of coins using the 3ds native number input
• refactored a little bit so the compiler has nothing to complain