Fail gracefully in ChainingProfileMapper.

Treat throwing sub-mappers as if had returned null (had no opinion about profile mapping).
UP-4290 add getAlternativeMaximizedLink() to IPortletDefinition.
UP-4291 getRenderUrl() is alternativeMaximizedLink when exists.
Refactor : Use syntactic sugar to get alternative maximized link.
[UP-4296] Add support for a 6 column layout.
Merge pull request #463 from apetro/UP-4291

UP-4291 MarketplacePortletDefinition renderUrl is alternativeMaximizedLink when available.
UP-4142 Importing local group changes updates cached entries

UP-4159/UP-4160 Importing local group changes updates cached entries
UP-4142:  Simplify import-membership_v2-6.crn by flattening the groovy
UP-4142 Improve groovy script and comments
Merge pull request #456 from apetro/sticky_profile_fail_gracefully2

UP-4285 Fail gracefully in ChainingProfileMapper.
Merge pull request #468 from jhelmer-unicon/UP-4296_6_col_layout

[UP-4296] Add support for a 6 column layout.