Minor gameplay changes and bug fixes

We decided to introduce this gameplay changes:

• Now you can heal sanity even if it've dropped to zero.
• The spawnrate of things now depends on the distance to campfire as well.
• Changes to flowers (spoiler)

  Their purposes were swapped and from now orange flower shows you the way to campfire, lights your torch and heals your sanity a bit, while blue flower leads you to quest item, heals you and your sanity a bit.
• Added experience indicator.

Bugfixes:

• Fixed bug with timer.

QOL:

• Added settings.