No need to split the instance methods of FieldString.
Added a LiteralString class for raw strings in statements.
Added support for between queries.

Defining predicates is now far more flexible. Every adapter has the
ability to transform the arguments list during condition building. It
does this through its `Translator` class.

Predicate definition now also allows the convenient definition of the
format and the argument transformation at the same time.

Literal strings can now make their way through condition building as
well.