Multi-Texture support

[Chimaine]

The MobTalker2 GUI should be able to display multiple textures at once.

There are several requirements for this to work properly:

1. Textures must be organized in groups, and only one texture of each group can be displayed at a time. This can be achieved by treating mobname as the group name.

2. An unlimited amount of groups can be displayed at once.

3. Textures of a group can be hidden with the hide command.

4. Scripts must be able to define positions for textures and the show command must accept either a predefined position or absolute coordines.

[Chimaine]

Merge branch 'origin/multitexture'

First step towards multiple textures, references #9

→ <<cset f26ffa93dd7d>>

[Chimaine]

Fully implement Multi-Textures, Fullscreen Textures and Texture Positions. Closes #9

→ <<cset 24529a121808>>