Binding generator v2 - augments fix #1

Binding generator v2 - augments fix #1

- group augments by target path and generate code
accordingly.

TODO #2 uses-augment
     #3 augmented choice-cases

Note: ignore some of failing existing tests
      until all work here is done

Explanation:

yang snippet

   container foo {
        leaf my-leaf {
            type string;
        }
    }

    augment /foo:foo {
        leaf bar {
            type string;
        }
    }

    augment /foo:foo {
        leaf baz {
            type string;
        }
    }

produces same generated code as

   container foo {
        leaf my-leaf {
            type string;
        }
    }

    augment /foo:foo {
        leaf bar {
            type string;
        }
        leaf baz {
            type string;
        }
    }

Change-Id: I2bdb3ecf22bf2cb72fab3080f2b40748775ba49b
Signed-off-by: Martin Ciglan <martin.ciglan@pantheon.tech>