ADD Spanish translation
MOD Standard keys (1-button-fire and spell)
ADD Spell implementation

- spell switching,
- sound for spell and teleportation
ADD Snakes in game
Update readme.txt
MOD HP text size is lower now
ADD Missing spanish labels (TODO)
MOD Add [ ] around a missing word
FIX Spanish missing texts
FIX Monster out of the game grid
FIX Poison does not affect armor
ADD Spell: Fireball
Convert TextMapper.h to UTF-8 encoding
TextMapper: Fix returning reference to temporary

TextMapper::getText() returns a reference.
Commit d98e41849f1b84d86ae394758f1bc5defdfbf05d makes it
so that missing entries get the string `"[" + key + "]"`.

This string lives in the getText function.
Returning a reference to it results in a dangling reference
after the function is finished.

This is undefined behavior, and causes a crash on my system.

This commit fixes this problem by returning a new string instead of
just a reference.