Expose field properties

- add choices to fieldHandler
- add widgetAttributes to fieldHandler
- add labelText to fieldHandler
- add errorText to fieldHandler
Update fieldHandler error getters

- remove validationErrors
- call validate from errorText
- remove errorText method from Field
Fieldhandler addtional `placeholder` property
Merge pull request #13 from JoeChapman/feature/expose-field-properties

Expose field properties