Feature/79 prevent invalid movement

[ChrisKrane]

Description

This PR will prevent players from moving anything when not their turn.
It also introduces a wincondition check, causing the game to end when a king is captured.

##Notes:
Also fixes a bug with rematch system

This branch also contains the solution from #77

Related Issues

Closes: #79

Changes Made

• Make game winnable when a king is captured
• Make players unable to move pieces when not their turn

Checklist

Check applicable items

• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented on my code where necessary.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.

[CraZyB1336]

LGTM!