Work In Progress - New Documentation

In this WIP branch, we are creating extensive documentation for the complete ValidForm Builder API.
This documentation will be written inline with each class and public method and auto-generated with PHPDoc.
The documentation should eventually be published as GitHub Wiki pages.

- [ ] Write Area documentation
- [ ] Write Button documentation
- [ ] Write Checkbox documentation
- [ ] Write Collection documentation
- [ ] Write Comparison documentation
- [ ] Write Condition documentation
- [ ] Write Fieldset documentation
- [ ] Write File documentation
- [ ] Write Group documentation
- [ ] Write GroupField documentation
- [ ] Write Hidden documentation
- [ ] Write MultiField documentation
- [ ] Write Navigation documentation
- [ ] Write Note documentation
- [ ] Write Page documentation
- [ ] Write Paragraph documentation
- [ ] Write Password documentation
- [ ] Write Select documentation
- [ ] Write SelectGroup documentation
- [ ] Write String documentation
- [ ] Write Text documentation
- [ ] Write TextArea documentation
- [ ] Write ValidForm documentation
- [ ] Write ValidWizard documentation