Feature/160/conditional settings

[pvrobays]

Closes #160

• [x] update Changelog
• [x] update Documentation in README
• [x] add ability to pass JS functions in the preferences object to the renderer
• [x] add ability to programmatically hide fields
• [x] add ability to programmatically hide groups
• [x] add ability to programmatically hide sections

Can be done with a new property on field, group or section items: hideFunction: (preferences) => { return true; }

[lacymorrow]

Nice work on this