Updates to Custom Level Editor — Spell Magic Steam update #387610

Updates to the level editor: Enemies can be added to custom levels. Added a button, in the build menu, for switching between editing and testing level. Upgrades menu can be edited to change player stats when playing custom level. Create custom artifacts in level editor. Place artifacts in custom level. Artifacts placed on grid will be available for player while playing custom level. Further work for sharing levels online was also done but is not yet available.