[Feature] Texture atlases support

[bnoazx005]

Description

Right now the engine has no built-in support of texture atlases. But even a few features in current version need them to store their data, e.g. fonts system.

So here TODOs list is:

• [x] Define a new interface ITextureAtlas and its base implementation CTextureAtlas, which is derived from CBaseResource.

• [x] Implement rectangles packaging algorithm.

• [x] Implement an internal engine's file format that will be specific for texture atlases. Right now we use YAML format for this purpose.

• [x] Implement loading of texture atlases from disk

[bnoazx005]

The current implementation of texture atlases is provided in 6c6dbb92278a458945e43c049f9fbd70069fff43 commit