add WatchEvent and WatchEventListener in order to notify following events :
- INDEXING, DOWNLOADING, UPLOADING
comment update
Merge branch 'master' into fix-watch-notif
Merge branch 'master' into fix-watch-notif

Conflicts:
	syncany-lib/src/main/java/org/syncany/operations/DownOperation.java
Merge branch 'master' into fix-watch-notif
Merge branch 'master' into fix-watch-notif
Merge branch 'master' into fix-watch-notif
deduper update
Merge branch 'master' into fix-watch-notif

Conflicts:
	syncany-lib/src/main/java/org/syncany/Client.java
Merge branch 'master' into fix-watch-notif

Conflicts:
	syncany-lib/src/main/java/org/syncany/operations/DownOperation.java
	syncany-lib/src/main/java/org/syncany/operations/Indexer.java
Refactoring
TODO : nice way to make link during upload between FileVersion and MultiChunk
Merge branch 'master' into fix-watch-notif