resolves yarddoc undefined refs and touches up default values for optional args

## motivation

```
$ be rake yard
[warn]: In file `lib/calabash-cucumber/core.rb':555: Cannot resolve link to label from text:
[warn]: ...{label | identifier}...
[warn]: In file `lib/calabash-cucumber/core.rb':448: Cannot resolve link to label from text:
[warn]: ...{label | identifier}...
[warn]: In file `lib/calabash-cucumber/utils/xctools.rb':63: Cannot resolve link to patch from text:
[warn]: ...{patch}...
[warn]: In file `lib/calabash-cucumber/tests_helpers.rb':5: Cannot resolve link to expected_mark from text:
[warn]: ...{expected_mark}...
[warn]: In file `lib/calabash-cucumber/tests_helpers.rb':31: Cannot resolve link to expected_mark from text:
[warn]: ...{expected_mark}...
[warn]: In file `lib/calabash-cucumber/tests_helpers.rb':31: Cannot resolve link to expected_mark from text:
[warn]: ...{expected_mark}...
[warn]: In file `lib/calabash-cucumber/launcher.rb':329: Cannot resolve link to :photos from text:
[warn]: ...{:photos =&gt; {:allow =&gt; true}...
[warn]: In file `lib/calabash-cucumber/launch/simulator_launcher.rb':377: Cannot resolve link to iphone from text:
[warn]: ...{iphone | ipad}...
[warn]: In file `lib/calabash-cucumber/launch/simulator_launcher.rb':442: Cannot resolve link to iphone from text:
[warn]: ...{iphone | ipad}...
Files:          38
Modules:        26 (   11 undocumented)
Classes:        10 (    3 undocumented)
Constants:      23 (   13 undocumented)
Methods:       358 (   77 undocumented)
 75.06% documented
```

Resolved all references.  All of them were `{}` outside of backquotes.