Binding DTO pattern enforcement does not honor 'modifier invert-match'

YANG 1.1 has defined a new construct under the pattern statement, which is the modifier-kind substatement. It has one defined value, invert-match, which instructs the engine to invert matching logic – only strings NOT matching the pattern are considered legal.

Binding codegen is ignorant of this change and produces positive match even when invert-match is requested.

Make sure BindingGeneratorImpl processes Pattern strings so that they become invert-matches when this modifier is present.