add activities tab
display current path in repo view
add create new dir
fixed a bug when refresh dirents
show loading animation when creating new dir
support loading more events
switch to related file/dir when clicking events item
fixed a bug of create new dir dialog
improve the way of passing the auth token to js

Call the setToken() function by:

   webview.loadUrl("javascript:setToken(TOKEN)");

so that we can pass the auth token into the js code
improve the way of passing the auth token to js
use http-request lib instead of raw HttpURLConnection
improve SeafConnection

We have to format the post request content manually when uploading a file,
because we need the content length in advance. Otherwise the whole post
request would be buffered in memory, which is not acceptable.
improve action bar title
fixed getFile

The file id should be from the server, not the local cached id
ensure the dirents is uptodate when entering a dir
getFile should return the latest file on server
add OpenFileDialog
fixed OpenFileDialog for device rotation
handle download task failed in OpenFileDialog
implement TaskDialog as a base class for some dialogs