Remove unused prefix from SimpleDataBinder

This was a remnant of early drafts of the binder and is not relevant to
the current impl
Added some basic javadoc

More docs coming
improve converters for new data binder

This commit removes the naive placeholder converters that we had in place for the new data binder and replaces them with an adapter which delegates to Spring's conversion service.
remove access specifier
clear up some structured editor code
minor javadoc change
parameterize BindingHelper
Copyright statements
fix failing i18n functional test
Merge branch '2.1.x' into 2.2.x
Merge branch '2.2.x'
fix failing STS test
Merge branch '2.1.x' into 2.2.x
Merge branch '2.2.x'
fix for GRAILS-9947 "Grails 2.3 forked mode classloading problem"
Merge branch 'master' of github.com:grails/grails-core
fix for GRAILS-9980 "In unit tests, make beans available in Grails mainContext"
Merge branch '2.1.x' into 2.2.x
Merge branch '2.2.x'
reactivate some tests