retry auto upload if it fails
handle the case when a cached file is replaced by the latest version

If a file was cached, and the version on the server is changed, the download of the
latest version would trigger a file change event. We work around this by save the
 time of the download, and ignore the immediate event triggered after the download.
fixed some cocurrency issue
[file mon] only handle file update broadcast
fixed photo/videos upload activity
fixed ShareToSeafileActivity when there are multiple accounts
fixed layout of multiple file chooser
do not show "modified" in file list
minor improvement of AutoUpdateManager
improve account login
provide drawables for different screen densities
upgraded version to 0.9.0
set list view backgorund to white
use progurad to shrink code size
load photos/vidoes from all possible default location

Camera photos and vidoes has diffent default locations on diffent phones.

* /sdcard/DCIM/Camera     (most Anroid phones)
* /sdcard/DCIM            (Lenovo A820t)
* /sdcard/DCIM/100MEDIA   (HTC 2.2)

We try to load all of them when choosing photos/vidoes to upload.
updated version to 0.9.1
fixed crash bugs reported on google play
update login api request
added maven pom.xml
update README