Fix type inferencing, syntax highlighting and code navigation for fields, methods and properties of Map-based types

[eric-milles]

For types that implement java.util.Map, Groovy offers specialized support for property access. Instance fields can only be referenced using the attribute operator (.@). Instance methods can be referenced through a call expression or method pointer/reference operator (.& or ::). Property access through the dot operators (. and .? and probably .*) creates references to map entries instead of fields, properties or methods. And the call operator (()) can also be used to retrieve a value and "call" the result.

Current IDE support for these many variations, including references inside closures that do not have explicit object expressions is a mixed bag (see below).

[eric-milles]