uploadFile by FileUploadEntity & OCTECT_STREAM
fix xUtils bug: ViewInjectInfo equal()
fix progress bug for file uploading fail
optimise
change message id & thread id & attachment id to int from long
serperate db op to DBOP.java
remove commented DB operations
optimise
resend failed file
add AttachmentLoader
support for downloading file
fix xUtils bug: ViewInjectInfo equal()
delete attachment when msg is deleted
refactor for ChatMsg & FileMsg, extending from DBMessage