Create a new entity. Simple entities can be constructed by passing a name,
value to the constructor; this creates a generic, plain entity reference.
For anything more complicated, you have to pass a Source to the constructor with the entity definiton,
or use the accessor methods. WARNING: There is no validation of
entity state except when the entity is read from a stream. If you start
poking around with the accessors, you can easily create a non-conformant Entity. The best thing to do is dump the stupid DTDs
and use XMLSchema instead.
Evaluates whether the given string matchs an entity definition, returning
true if so, and false otherwise.
Returns the value of this entity. At the moment, only internal entities are
processed. If the value contains internal references (IE, %blah;), those
are replaced with their values. IE, if the doctype contains:
<!ENTITY % foo "bar">
<!ENTITY yada "nanoo %foo; nanoo>
then:
doctype.entity('yada').value #-> "nanoo bar nanoo"