document @RestController annotation

Issue: SPR-11119
Minor polish around @RestController
Add getting started
Remove iBatis and name-check Spring Data
Drop SqlMap prefix following iBatis rename
Remove references to webwork
Add some more TODOs in what's new
Polish
Document meta-annotations
Add servlet 3.0 info to "Initial web configuration"
Remove refs to Tiles v1
Polish to always use NOTE callouts
Update JRuby and Groovy versions
Restore image widths SPR-11143