[utils] provide a better applet_log function

don't double check log_level

check if message is null point before dereference it

use macro BUFSIZE to replace hardcode 1024
[message-listener] reformat apple-specific code and eliminate coverity warning

eliminate coverity warning

    Explicit null dereferenced
[notification-monitor] move the construction procedure of QTimer to the constructor
cleanup code which is causing Wsign-compare warning
Merge pull request #237 from Chilledheart/patch-7

[message-listener] reformat apple-specific code and eliminate coverity w...
Merge pull request #236 from Chilledheart/patch-8

[notification-monitor] move the construction procedure of QTimer to the ...
Merge pull request #235 from Chilledheart/patch-9

cleanup code which is causing Wsign-compare warning
Merge pull request #231 from haiwen/patch-5

[utils] provide a better applet_log function
added file browser
[filebrowser] implement file browser
rewrite filebrowser based on fbrowser_ch
remove debug messages
handle http redirect
handle readonly library
improve code about getting local cache file path
[filebrowser] show error message when error happens
show error message when upload fails
handle encrypted library
open cache folder
remove the old version of a file when downloading the newer version