Enhance arethusUtil.toAry()

Handle undefined param and return [] for it.
Handle preselections in treebankRetriever
Refactor state.replaceState

Takes an optional second param which can keep token selections.
Used when retrievers declare preselections.
Use retriever.preselections in state
Update conf files
Todo comment in treebankRetriever
Merge pull request #194 from latin-language-toolkit/preselect_on_retrieval

Preselect on retrieval