Version 1.9.1: UI Rework, polish, and more

A small patch to make the game more user friendly.

New Item : Essence Spell
New Craftable : Shadow Core
New Feature : Shadow Minon Spell can be upgraded
UI Changes : Bank chest now shows prompt always, Inventory now split by categories, Shadow Minion now has HP bar and damage display, Map select and delete button no longer shows when no map selected
Bug fixes : Map now autosaves on creation, invincibility spell now has corrected description

This update brings a decent change to the user interface of the game's inventory. Buttons were moved around, and the inventory is now split into categories so it's less messy. The bank chest UI also has a small rework to make it more intuitive for players. The main menu map selection button were also changed a bit in order to point some lost sheeps in the right direction when they don't have any maps to select.

Additionally, this update introduces the essence spell, which is a spell for making magic dust, a valuable yet rare material. Now, grinding is no longer the only way to get this material as you can create it with the essence spell. This makes gathering essence more user friendly.

Although the shadow minion spell was already fun, it has been decided that it will be made more fun. Now the spell can be upgraded to increase your minion's max health ... infinitely. This can be done with the Shadow core, another recipe you will now have to discover.