world.js: Refactor move commands out of keyDown

In order to better handle move commands, refactor them out of the keyDown
event handler. This will enable using other input methods to trigger a move
command, such as mouse clicks or touch events.
world.js: Trigger movement with clicks on the map

Clicking on the map in different quadrants will move you in that direction.
Clicks are measured relative to the centre of the current location centre of
the map. Click above the player to move up, click below to move down etc.

This should enable better gameplay on touch devices.
Adds link to play game online
Add an 'eat meat' button to the loot screen

When I played this, I would often madly try to click the 'eat meat' button
after I won a fight, only to have the 'leave' button appear in its place,
causing me to lose my chance at both healing and looting.

This patch adds an 'eat meat' button to the loot screen to avoid this UI
problem.
Added max/zero buttons to worker assignment and expedition supply packing to prevent eg having to click 50x to fill food supplies.
Fixed non-combat meat eating