fixed a bug causing cpu usage even when idle
added file browser
[filebrowser] part 2
[filebrowser] small fix
[filebrowser] small fix2
[filebrowser] add download-mgr
[filebrowser] part 3: add SeafileNetworkTask
[filebrowser] remove virtual keyword from networktask
[filebrowser] add networktaskbuilder
[filebrowser] small fix3
[filebrowser] small fix4
[filebrowser] fix existing file issue
[filebrowser] small fix5
[filebrowser] add backward and forward buttons
[filebrowser]small fix6
[filebrowser] small fix7
[filebrowser] small fix8
[filebrowser] use a worker thread to do download tasks
[mac] fix build with qmake
[filebrowser] move network