Update Jackson to 2.4.3
ISIS-537: tidy up in ActionLinkFactoryAbstract and ActionPromptProvider (throw IllegalArgumentException rather than NPE).
ISIS-537: moved all CSS from components that provide additional CSS into PageAbstract.css

The remaining subclasses of PanelAbstract that were overriding renderHead(...) to explicitly contribute its CSS no longer do so; and their CSS instead has been copied into PageAbstract.css.

Also:
- moved algorithm to locate CollectionSelectorProvider from component hierarchy into a Util class (similar to ActionPromptProvider)
- removed the (unused) TabbedPanelAbstract; this will need re-implementing anyway using bootstrap.
ISIS-537: deleting unused panel CSS; moving all CSS in PageAbstract instead into bootstrap-overrides.css.
ISIS-537: CollectionContentsAsSummary icon now uses fa- icon.
ISIS-961: in IsisTransactionManager, call setAbortCause if an exception is caught for any reason (this includes an exception thrown by domain object code).

Also:
- minor enhancement/improvement to error page so that a NonRecoverableException's message is displayed rather than a generic message.
ISIS-961: removing duplication between ActionLinkFactoryAbstract and ActionPanel (functionality moved to ActionModel)
Merge remote-tracking branch 'martin-g/jackson-2.x-update'
ISIS-537: tiny fix, adding final modifier, per code review