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
Refactor sidepanelFolder
Make sidepanelFolder configurable

Receives an init() function and reads in its initial fold status from
the configurator.
Hide sidepanel per default in staging.json
Merge pull request #195 from latin-language-toolkit/fold_status_of_sidepanel

Fold status of sidepanel
Extract saving to own service called saver
Refactor saver
Add saver directive

Only shows the element when something can be saved and is able to save
on click.
Merge pull request #197 from latin-language-toolkit/extract_saving

Extract saving
Update and refactor MainCtrl spec

Whoops, #197 broke that spec. Used the opportunity to refactor the file
a bit.
Add mode as standardProperty to configurator
Refactor standardProperties
Add default mode for all configs in configurator

The global default mode is 'editor'.
Change heads only when requested in state

The selectToken function takes an additional param to announce the
possibility of a head change now.