Fail fast if any of the compound names contains a colon (`:`)

Imagine what happens when we get

```
$scheme
 [...]
 // Harmless, huh?
 B -> E# -> H -> L# -> M:RNH2
 [...]
$compounds
 [...]
 // Actually eats your brain out 🤯
 M:RNH2: 0w/M/product_0.out
 [...]
```

Pretty bad.