fix a font issue with qt4.x under yosemite
Merge pull request #328 from haiwen/fix_mac_font_issue_under_yosemite

fix a font issue with qt4.x under yosemite
Update version to 4.0.2.
apply minor improvements on the words of coments
add initial support for dropping file through repo tabs

- copy the dropped file to the worktree if the repository is synced
- add progressdialog for the mainwindow uploading
- don't bother the user if he (or she) cancels the uploading task
- support encrypted repos now
copy task is assigned to another thread (from global threadpool)
update translations
[filebrowser] auto upload if cached files changed
refresh file browser dialog when file auto updated
get_repo_list can be NULL when no local repos yet
Merge pull request #319 from haiwen/drop_file_through_repo_tabs

add initial support for dropping file through repo tabs
reverse using ServerRepo as FileNetworkTask ctor param
accept the drop event on repo tree view
add initial support for upload directory