Faster map loading, and morale in battle

A summary of the changes over the last few months.

Front end:

• Removed menus that weren't needed.
• Fixed cancelling an army's movement.
• New quick-menu icons for armies and cities.
• A smaller army icon on the map.
• Fixed the "time left" shown for building and troop training.
• Updated the NPM dependencies.
• Battle results when you attack a city.
• Fixes to the mobile site.
• The navigation is updated and grouped into categories.
• Game assets preload in the background: the map loads in under 2 seconds instead of over 30.

Back end:

• Morale counts in the power calculation.
• Fixed the notification when a city is taken over.
• Several world maps made for testing.
• A server speed constant, for quicker testing.
• A lot of refactoring.