Tor circuit screenshots

Screenshots for !69 (merged)

Adds the "screenshots" directory to tor-browser branch.

Add screenshots for tor circuit.

screenshots/tor-circuit-file-menu.png is for:

• menu-new-tor-circuit. Shows the accesskey and uses title case.

screenshots/tor-circuit-app-menu.png is for:

• appmenuitem-new-tor-circuit. Uses sentence case.

screenshots/tor-circuit-toolbar.png is for:

• toolbar-new-tor-circuit. Uses sentence case and has a tooltip.

screenshots/tor-circuit-panel-plain.png is for:

• tor-circuit-panel-heading
• tor-circuit-panel-node-list-introduction
• tor-circuit-panel-node-browser
• tor-circuit-panel-node-region-guard
• tor-circuit-panel-new-button
• tor-circuit-panel-new-button-description-guard

screenshots/tor-circuit-panel-bridge.png is for:

• tor-circuit-panel-node-typed-bridge
• tor-circuit-panel-new-button-description-bridge

screenshots/tor-circuit-panel-vanilla-bridge.png is for:

• tor-circuit-panel-node-bridge

screenshots/tor-circuit-panel-tor-onion.png if for:

• tor-circuit-panel-alias
• tor-circuit-panel-node-onion-relays

screenshots/tor-circuit-panel-unknown-region.png is for:

• tor-circuit-panel-node-unknown-region. Shows the "Unknown region".