Fix syntax coloring fallbacks for disabled preferences

[eric-milles]

Currently supported: if editor syntax color preference Abstract Classes is off, abstract class references are highlighted using syntax coloring preference Classes. Also slashy strings fall back to strings.

Unsupported fallbacks (disabling preference on the left results in default coloring):
method declaration -> method
static method invocation -> method
static final field -> static field -> field
parameter declaration -> local variable declaration -> local variable reference
annotations -> default (GroovyTagScanner does not support disabled for color preference)

Unimplemented semantic highlighting (left hand side):
local variable declaration -> local variable
abstract method call -> method
inherited method call -> method
inherited field -> field
type argument -> type kind
auto(un)boxed expression -> expression kind