Windows compatibility improvements, add tab_id filter to bt text, add --focused to bt activate (Pr/21/master)

[balta2ar]

• add "--target" argument to disable automatic mediator discovery and be able to specify mediator's host:port address. Multiple entries are separated with a comma, e.g. --target "localhost:2000,127.0.0.1:3000"
• add "--focused" argument to "activate" tab command. This will bring browser into focus
• automatically register native app manifest in the Windows Registry when doing "bt install" (Windows only)
• detect user's temporary directory (Windows-related fix)
• use "notepad" editor for "bt move" command on Windows
• add optional tab_ids filter to "bt text [tab_id]" command