add save and load option

[stolsky]

serialize current act

• [ ] id of current Act
• [ ] id of active hero this.#activeHero.getId()
• [ ] id of current scene this.#currentScene.getId()

serialize GameCache

• [ ] serialize flags: id, value
  • list of ids and values: ["flag1ID:value1", ... ]
• [ ] serialize all heroes
  • inventory -> ids, order!
• [ ] serialize all items
• [ ] serialize all scenes
  • id, intro, ids of elements: [<string>,<0|1>,<string>] -> example: ["sceneID",0,"elem1ID,elem2ID,elem3ID,..."]
• [ ] serialize elements/items (BaseObject)
  • save the id, the list of all changes (memory of states occurred) and the action states
  • "action state" is just the id + index of left + index of right actions list separated by comma
  • 1,0,2 means, select the state with id 1; select the first left action; select the 3rd right action (indices are zero based)
• [ ] serialize all dialogs
  • planning on how and what to save

removed objects and those that have not yet been interacted with

• [ ] don't serialize removed objects
• [ ] serialize only the id for untouched objects

Serialize Log

• [ ] save all text from log

[stolsky]

similar to #10. will be in the same merge request.