A context Term is part of an expression, a Literal or a Symbol,
where a literal is something that cannot be resolved further,
and a Symbol is a substring bracketed by ${ and }, which can
be resolved.
Parse a string or substring, returning a sequence of Terms,
where a Term is either a Literal (which cannot be parsed
further) or a Symbol, something enclosed in braces (which
can be parsed further).
The Template consists of two Strings, the first of which should
resolve in the Context to an object and the second of which is
the name of a field in the class of which the object is an instance.