Refactor: render URL as property of MarketplacePortletDefinition.

Moves responsibility for computing render URL of defined portlet into `MarketplacePortletDefinition`, from portlet JSPs.
Adds utility method to `PortalWebUtils` to get request context.
Drops deepLink from model in favor of the renderUrl property of the `MarketplacePortletDefinition`.
Improve getRenderUrl JavaDoc.
Refactor: zap stray local variable, mark final.
Related portlets are MarketplacePortletDefinitions.

Instead of `IPortletDefinition`s.
Trivial: Specify type of category set members.
Refactor: move featured portlet determination to service layer.
Trivial: fix saveRating JavaDoc.
Merge pull request #319 from apetro/marketplace_refactors_from_servlet_links

Marketplace refactors from servlet links