Implementation of a chess board editor

[programarivm]

A chess board editor needs to be implemented for users to easily create chess positions. This component may entail a variaty of tasks, so let's try to break it down into smaller parts.

• Drag and drop functionality #24
• Display the FEN string #27
• Allow to delete pieces #28
• Set up the castling ability #29
• Set up the turn to play #31
• Flip the board #32
• Clear the board #34
• Starting position #35
• En passant square #37