Binding generator v2 - uses statement - uses inner type #2

Binding generator v2 - uses statement - uses inner type #2

- for current implementation of yangtools does not copy "types" from groupings,
but the original definition of a type is reused, so we should find inner type
added by uses by original node.
  this patch should be merged with:
  - https://git.opendaylight.org/gerrit/60529
  - https://git.opendaylight.org/gerrit/60582
- support uses leaf with inner type union, bits
- add yangs and test

Change-Id: Ibee57eb030a79e6ce06bb371e82257b7ab58ab98
Signed-off-by: Jie Han <[email protected]>