Browse lexicon dashboard

Added a dashboard to browse and edit/clean the lexicon. Currently it displays lexical items/nodes in alphabetical order (its configurable by changing the Lexicon.js sortBy parameter). It uses the new lexicon map reduce which automatically builds lexicon tuples based on datum and assigns a confidence level for whether a lexical item was correctly generated. https://github.com/OpenSourceFieldlinguistics/FieldDB/pull/1411