Replace drop tracking system
Fix a syntax error
Merge pull request #9 from m101010ax/pushes

Pushes
Merge from the branch 'develop-drops'
Add 'Happy Pills' to drops display list
Remove obsolete difficulties
Fix an accidental error that is added when resolving conflicts
Add HV Font text parser
Add supports of HV Font
Fix a regression of 'Warnings before starting Challenges'
Refactor 'inventoryWarning' and fix the position of warning icon
Integrate the role of `inventoryAlert` into `hvStat.characterStatus`
Refactor 'hvStat.database.openIndexedDB'
Refactor 'hvStat.database.maintainObjectStores'
Increment database version and implement creation of new object stores
Implement storing of item/equipment drops
Implement display of equipment drops
Implement display of item drops

* Arrange the configuration of `ItemDrops` and `EquipmentDrops` in order
  to extend roles
Integrate the function of `Arena Rewards` tab into `Drops` tab
Remove 'Arena Rewards' tab