Implement `has property` shared example.

Current spec status:
- 2.0: 352 examples, 0 failures in 0.103 seconds.
- 2.1: 418 examples, 0 failures in 0.12292 seconds.
Alias property matchers as `should have …`.

Current spec status:
- 2.0: 358 examples, 0 failures in 0.12074 seconds.
- 2.1: 424 examples, 0 failures in 0.12821 seconds.
Refactor out SharedExampleGroup concern.

Current spec status:
- 2.0: 358 examples, 0 failures in 0.10372 seconds.
- 2.1: 424 examples, 0 failures in 0.12452 seconds.