Atom types in error messages are missing the leading ":"

[emilsoman]

This is because we depend on to_string to print types and that removes : from atoms. One easy solution could be - parse atom types as strings and store them as ":foo" instead of :foo.

[polvalente]

@emilsoman this solution is good, but I think we should convert the atom to string only after "instantiating" the atom, so we fill the Atom Table properly. Otherwise, it might be the case in which the compiler handles a program which will always crash due to overflowing the Atom Table