ISIS-1976: removes OA map, stream for metamodel, excising guava
Key achievements:
Metamodel: almost all guava Function and Predicate idioms removed
Metamodel: slight API improvements, such that some of the internal meta-data that is kept in Java
Collections is no longer copied into immutable lists for any calling client, instead Java Streams are returned (which treat the underlying collections un-modifiable by design)
the ObjectAdapter per-session map/cache is history
the legacy modules have been removed, for convenince and ease of migration the legacy/
transition-1-2- module remains and shall provide legacy glue code
shiro was moved to plugins, and its artifact renamed, to be inline with the other plugins