Removed menu_selector_load_game; we can set custom events via FFL and do not need to maintain several versions of the same object.
Normalized the behaviour of the heart object and the mana cube wrt restoring Frogatto.
→ Mana cube now restores mana in the effect object, to make reuse easier. This fixes fountains and coolers not restoring mana, but displaying the mana restore effect.
→ The heart now uses player_controlled.heal(hp), which behaves somewhat like setting mana in that it constrains the heals to not exceed max_hitpoints. (This used to be coded in the heart, but we are planning to have more healing items.)
Mana is directly settable because we have the option to define a custom accessor for it.