Finished rest of the game

This pull request requires the latest media from https://bitbucket.org/chessmasterhong/wateremblem-media/downloads, and finishes the game (well, in one sense).

In all seriousness, this pull request contains the following changes:

Implemented one new map, edited the Big Castle map from the demo as a final map.
Set up bosses and randomized their stats for some interesting battles.
Added two new terrains, snow and throne.
Added some new exclusive items for bosses.
Properly set up the seize objective, where the player seizes the throne.
Set up all maps with enemies.
Set up main.js with the level progressions and music for each map.
Reset some test stats for players (reverted item catalog weapons to actual stats, decreased player movement from 12).
Extended the shop items.
Set up enemy spawner to include new boss and enemy groups.
Fixed issue #170, where the enemy phase music would play after battle, despite having more player units to move.
Prevented player from attacking/counter-attacking with a staff equipped.

chessmasterhong / WaterEmblem