Resources aren't located in resources/ folder(s)

[MathRPG]

Resource files are scattered throughout the code, and are not (as one might intuit) located in their designated resources/ folder.

TODO:

• Understand .getClass().getResource() idiom, and potential alternatives
• Introduce class to abstract 'resource' management
• Move resources to their folders

Relevant resources:

• arquivo/xml/dtd
• gui/{html, imagens}
• idioma, potentially
• JavaFX and other forms, when introduced
• Text templates, if ever extracted