replace zxing with NuGet pkg

Squashed commit of the following:

commit e280c2385c
Merge: 579039f 87aa9eb
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Wed Mar 16 04:02:27 2016 -0400

    Merge remote-tracking branch 'origin/master'

commit 579039fe40
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 21:45:23 2016 +0800

    log unhandle exception

commit 8d863f1d5f
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 21:44:54 2016 +0800

    fix Availability Statistics

commit b3ce1c698a
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 21:07:54 2016 +0800

    tiny refactor

commit 0f7d39e27e
Merge: bd7078a b01aced
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 20:02:58 2016 +0800

    Merge remote-tracking branch 'origin/master'

commit bd7078aa4f
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 20:01:58 2016 +0800

    tiny refactor

commit 49adb95b6e
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 03:44:26 2016 -0500

    log more Ping information for debug

commit 2aa0620ddd
Author: Gang Zhuo <gang.zhuo@gmail.com>
Date:   Fri Mar 4 03:04:10 2016 -0500

    reduce 3rd packages

[solve conflicts and squash to make history clean]
Signed-off-by: Syrone Wong <wong.syrone@gmail.com>

# Conflicts:
#	README.md
#	shadowsocks-csharp/Controller/Service/AvailabilityStatistics.cs
#	shadowsocks-csharp/Controller/Service/PACServer.cs
#	shadowsocks-csharp/Controller/Strategy/SimplyChooseByStatisticsStrategy.cs
#	shadowsocks-csharp/Data/cn.txt
#	shadowsocks-csharp/Model/Configuration.cs
#	shadowsocks-csharp/Model/LogViewerConfig.cs
#	shadowsocks-csharp/View/LogForm.Designer.cs
#	shadowsocks-csharp/View/LogForm.cs
#	shadowsocks-csharp/View/MenuViewController.cs