Custom hotkey for switching between tabs

[jwhitmore]

Create configurable hotkey for switching between tabs.

[TheCodeArtist]

Based on terminal emulators like Gnome-Terminal, and window mangers like i3,
i find the following the most empowering and intuitive Keyboard hotkeys:

• CTRL+1/2/3/.../N to switch keyboard focus to Nth open tab.
• CTRL+ up/down/left/right to switch keyboard focus to an open tab in that direction from current tab.

To avoid conflicts with any of the users' existing custom keyboard shortcuts,
a setting option could allow users to choose ALT or Super keys instead of CTRL in teh above combinations.