Enhance model info to support better model description

[brynrhodes]

To better support CQL authoring, ModelInfo should be enhanced to include additional metadata about the model. Specifically:

• label - A string user-friendly label for the element
• definition - A markdown definition of the element
• comment - A markdown comment for the element
• bindingStrength - required,extensible,preferred,example
• bindingValueSet - url of a value set specifying possible values
• constraint - ConstraintInfo { name, severity (error|warning), expression (CQL w/o retrieves, parameterized by Value of the type of the element), message }
• mustSupport - A Boolean indicator of mustSupport

[brynrhodes]

Addressed in the 1.5.2 release