Fixes in vk service
Updated auth dialog:
    Added vk icon
    Fixed grammar errors
Fixed multiple dialog opens.
Search speed has been accelerated
Fixed unhandled exception on DBus service.
Fixed app freezes on attach new tab/close exists tab
Added excepthook
Fixed issue #437
Fixed incorrect dran'n'drop tracks adding from VK.
Small PEP-8 fixes.
Added vk pixmap