Add an example use of FXFormFieldValueTransformer to the BaseExample

Note that this PR depends on the bugfix in PR #17
Improved setter logic for form
Merge branch 'master' of https://github.com/nicklockwood/FXForms
Merge pull request #18 from bartvandendriessche/example/NSValueTransformer

Add an example use of FXFormFieldValueTransformer to the BaseExample
Merge branch 'master' of https://github.com/nicklockwood/FXForms
Added FXFormFieldValueTransformer example
Added missing setter case logic
Merge remote-tracking branch 'upstream/master'