add random monsters to battle

- monsters should be randomly encountered, checked by rolling dice transparently for every tile the player moves to.
- on an encounter, the scene should switch to a battle with a turn-based menu system
- amount and type of monsters are specific to a particular area of the game
- monsters should have at least the following attributes: hit points, magic points, attack, defense, magic attack, magic defense, items, experience value, items available, spells available

NAME: [ name of creature ]
TYPE: [ humanoid, monstrous, animal ]
TERRAINS: [ ice, plains, forest, hills, jungle, mountains, swamp, desert, volcanic, air, underground, space, water ]
FREQUENCY: [ unlikely: 1%, rare: 5%, uncommon: 20%, common: 50% ]
NUMBER: [ number of followers of same type ]
TIME: [ any combination of morning, day, night ]
TREASURE: [ any combination of: gold, items, experience ]
FEAR: [ percentage]
HP: [ amount of hit points ]
MP: [ amount of magic ]
ATTACK: [ percentage ]
AGILITY: [ ratio to human ]
DAMAGE: [ dice + mod ]

An example monster:

NAME: Slime
TYPE: monstrous
TERRAINS: plains, forest, hills, jungle, mountains
FREQUENCY: common
NUMBER: 1-3
TIME: morning, day, night
TREASURE: 1 gold, 2 experience, 5%: healing leaf
FEAR: 10%
HP: 10
MP: 0
ATTACK: 80%
AGILITY: 1
DAMAGE: d4 - player defense

example monster explained:

- The slime is a monster. (no reasoning for its actions).
- There is a common chance (50%) it can be found in the plains, forest, hills, jungle, or mountains. If other monsters are common in the given area, another chance is rolled to see which)
- 3 sided die is rolled for number appearing
- appears during any time of the day
- upon slaying, leaves 1 gold, 2 experience points, and a 5% chance of a basic healing item
- 10% chance of running away on it's turn (if injured)
- Has 10 points of life
- Has zero magic
- Chance of attack succeeding is 80%. If the player has a defense of 50%, this means it's modified attack chance is 30%.
- Damage dealt is 1-4 minus player's defense.