remove CRC and detecting duplicate document
DocumentFile: factory: only check for mime for plain text
DocumentFile: remove abstract
DocumentFile: factory: return DocumentFile as default doc
DatabaseCollection: iterable
Indexer: new documentIterator method
DocumentFile: add file size
Indexer: add reindex parameter to updateDocument
WatcherThread: new watcher

- rename doesn't work (problem: no CRC)
add IndexData class
IndexData: add document last id
Terms: rename crc to docId
update indexer and document collection
WatcherThread: move common docPathToId operation to methods
WatcherThread: complete everything
Terms: fix when removing document
WatcherThread: move WATCH_STOP handler
Indexer: add factory function
Term collection: update term collection
App: add some log messages