Support marketplace service long description with rich text format

Detailed Description

As a service author, in order to provide detailed steps on how to use my service, I need my service description to include rich text formatting such as

• bullets (currently OSB specified bullets only appear in service plans)
• <code> format in order to display
  • CLI cli code fragments cf create-service -c {...} and cf bind-service -c {...} or cf map-route service ...
  • sample VCAP_SERVICES format and output
  • Short code snippets for using the services (SDK, or API calls)
• image reference to show architecture diagram explaining client usage such as the following explaining how a cassandra service gets used by its driver
• multiple hrefs for different aspects that would complement existing documentation and support urls

Context

This feature would help developers better understand their marketplace offers.
This feature may at times avoid service authors to serve independent documention, and instead include their documentation in the new rich text long description.

Possible Implementation

Service brokers return an extra field that augments the current OSB service meta-data that contains rich-text formatted content.

Possibly, the rich text format could be markdown, i.e. http://spec.commonmark.org/
There seems to have a wide range of markdown renderers such as https://github.com/markdown-it/markdown-it

Start by reviewing the OSB service metadata fields linked in the issue and the marketplace service-description handling in Stratos. Compare the proposed CommonMark approach with available Markdown renderers. Done would mean service brokers can provide rich text that the marketplace displays with bullets, code, images, and multiple links.