Update to 2.1.1

Changelog:
Release 2.1.1 Februrary 10th 2016

    UI improvements for HiDPI screens, error messages, RTL languages
    Fix occurences of "Connection Closed" when a new unauthenticated TCP socket is used
    Fix undeliberate WiFi scanning done by Qt Network classes
    Several fixes/improvements to the sharing dialog
    Several fixes/improvements to the server activity tab
    Create the directory when using --confdir and it does not exist
    Windows Overlay icons: Fix DLL and icon oddities
    Mac Overlay icons: Don't install legacy Finder plugin on >= 10.10
    Linux Overlay icons: Nemo plugin
    Overlay icons: Fix several wrong icon state computations
    Allow changeable upload chunk size in owncloud.cfg
    Crash fixes on account deletion
    Forget password on explicit sign-out
    OS X: Fix the file system watcher ignoring unicode paths (#4424)
    Windows Installer: Update to NSIS 2.50, fixes possible DLL injection
    Sync Engine: .lnk files
    Sync Engine: symlinked syn directories
    Sync Engine: Windows: Fix deleting and replacing of read-only files (#4308, #4277)
    Sync Engine: Fixes for files becoming directories and vice versa (#4302)
    Misc other fixes/improvements

(ryoon)