Refactor Graphics plugin architecture

[adamyaxley]

Instead of implementing various classes such as Texture, Text, Map etc simply implement only one class which has simplified callbacks for rendering such as:

• createContext()
• destroyContext()
• createTexture(std::shared_ptr<Texture>) - creates a native texture object and stores it in the Texture::m_userData
• destroyTexture(std::shared_ptr<Texture>) - destroys the native texture object stored in Texture::m_userData
• drawQuads(std::vector<Quad> quads) - draws quad vertices, transforms and texcoords
• reset() - resets the state and gets ready for another frame

[adamyaxley]

Dear ImGUI has a ImDrawList::AddImageQuad that could be used for Sprites, Maps and potentially Text too. Text could directly use ImGUI's text functionality.