Renders a custom field.
Possible types:
Currency - A currency field
Date - A date and time in the format 2012-09-12 09:50:20
Email - An e-mail address
Enum - A enumerated (i.e. decision) field
Location - A physical location (e.g. mailing address)
Number - A numeric value
Phone - A phone number
String - A plain, short string
Text - A longer string
Url - A URI