Add SimpleAnnotationMeta classes and readers
Replace the existing ASM based readers with new implementations that
also support MergedAnnotations. The meta-data classes themselves are
now immutable, and constructed via separate reader classes.
The `SimpleMetadataReader` class has been updated to return the new
classes, however the old ones remain since some of them are public
and might be being used directly.
Support String->Class adaptation in MergedAnnotation
Update TypeMappedAnnotation so that Strings can be used to represent
Class attribute values. This will allow ASM annotation readers to
present a `MergedAnnotation` instance without necessarily having the
actual class values on the classpath.
When the underlying value is a String, any calls to
`getValue(name, String.class)` or `asMap(Adapt.CLASS_TO_STRING)` will
simply return the original String. Calls that need the actual Class
result (such as `getClass`) will use `Class.forName` and may throw
a `ClassNotFoundException` at that point.
This commit also allows an empty Object to be used to represent
any empty primitive array.