Build form inputs

[nicdford]

[nicdford]

Largely completed by #72

For future release:

• Create JS package to further features including the ability to use labels as placeholders (similar to how material design handles theirs)
• Create JS package to allow full control of select elements
• How do we handle error message styles, as they are going to largely be tool/implementation specific

[nicdford]

Feedback from group to add:

• File upload field styles
• Add example of form validation
• Date/time input styles
• List option (in gravity forms)
• Gravity wiz nested fields (in gravity forms)
• Page styles / progress bars (in gravity forms)