BioSQL support in Jython
Newick writer should enclose node labels in quotes if necessary; write node comments in square brackets.
Only surround a label with quotes if the label is not empty.
Converting a tree into a librdf model and then serializing is slow, requires a lot of memory, and is not feasible for large trees. Refactoring CDAOIO.Writer to write triples directly to file instead of using librdf. This also makes the API more similar to other Bio.Phylo modules.
Default tree URI is blank, but still create a tree object.
Merging with origin/cdao.