Switching feature

[yas-mnkornym]

Added a feature to switch between virtual desktops by additional shortcut keys.
A screenshot of the updated settings dialog is available here: http://t.co/u24QnGsfrp

[Changes]

• Add 2 shortcut settings
  • SwitchLeft (Default: N/A)
  • SwitchRight (Default: N/A)
• Add GetLeftDesktop() and GetRightDesktop() private methods to HookService class
• Add if conditions to KeyHookOnPressed() in HookService class to handle SwitchLeft / SwitchRight
• Add "Switch virtual desktop" section to "Shortcut key" section in settings dialog

[Tests]
Manual tests

• Set shortcut keys to switching feature, verify desktop is switched by the shortcut keys.
  • with "Loop" option enabled/disabled
• Verify default shortcut keys (Ctrl + Win + <-/->) still work correctly.