Referencing Binary Format: Remove references to collections

[wjnicholson]

Currently BeanReferences increments counts for values that are collection types, when we never serialize references for collections.
Doesn't affect serialization massively, but without we could be using a smaller references array / more efficient reference numbers. e.g in the test example, previously the letters "A" and "B" used references 5 and 6, rather than the 1 and 2 that they should have been (as the most common item to be referenced).

Can't really change the code to reuse collections, as some types of collections are a bit hairy, what if it's first read as Set but later we serialize a SortedSet with the same elements? Can't reuse the original value but instead need a copy constructor, and that's a lot of effort to code.
If somebody really wanted that effect they could wrap the collection in an ImmutableBean and get the deduplication for free.