1.13 minor improvements:

[elidupree]

• Use wesnoth.is_local (and wesnoth.get_viewing_side?) instead of my hacks
• Use wesnoth.is_fogged and wesnoth.is_shrouded
• use side.net_income in the mana/gold theme UI
• investigate wesnoth.show_menu?
• Tunnels (cats and Portals) can now permit exiting through allied units
• use an effect with apply_to = alignment instead of setting alignment directly
• apply_to = new_advancement and remove_advancement might be useful for some things
• use the new unified leadership ability instead of my customized version
• use new image-path functions (especially different scaling in the customize-appearance menu?)