Add spell casting system

[M0rica]

This PR adds a spell casting system to let a player cast spells without needing to type in a command.
How it works:

• Cast a spell:

  When a player is holding a stick with the custom name "Magic Wand" in the main hand while sneaking, the system records a point where the player is looking at. Now the player moves his head to draw a pattern in front of him. Once the player stopps sneaking, the system analyses the pattern and tries to map it to a known pattern which will cast a spell. A pattern consists of an infinte sequence of lines with each line being one of 8 types: up, down, left, right, up-left, up-right, down-left or down-right.

• Bind a spell to a custom pattern:

  To bind a spell to a custom pattern, the player needs to typ in the command /spell bind <SpellName>. Now the player just needs to draw the pattern he wants to bind the spell to and after that, the custom pattern will trigger the spell. It is possible to bind the same spell to multiple patterns, however binding a spell to a pattern bound to another spell will override which spell is bound to the pattern.