Add some value to high Mana pools

Improved fix to [this HabitRPG issue](https://github.com/HabitRPG/habitrpg/issues/2069). Day rollover now gives the better of 10 MP or 10% of max MP. Mana drip from To-Dos gives the better of 1 MP * (task + checklist items) or 1% of max MP * (task + checklist items).

Gives some actual utility to high Mana pools--bank space tends not to be much of a concern unless the user is away for some time.