Switch to BTreeMap for storing JSON objects
(Reference BTreeMap in documentation ...)
Replace collections that have moved out of tree

* TrieMap and TrieSet are gone
* TreeMap and TreeSet are replaced by BTree variants
Use the `BTree*` variants ...
Farewell to the `Trie` collections ...
Merge pull request #3 from drbawb/feature/fix-collections

Update collections which moved out of tree