Revised boss mechanics

Now the boss fight is less frustrating. Before entering the boss a message will appear advising the player the loss he can have by entering the boss fight.

The next changes were made:

• Boss attacks will kill only the 2 allies.
• Boss will attack only the allies with less numbers so the gap of experience when you loose them isn't that frustrating.
• Boss button won't appear during boss fight, avoiding a boss dialogue endless loop bug that was happening.
• New option in the pause menu that allows players to hide the monsters' dialogues.