Allow files with plaintext content to be rendered in the viewer

[GoogleCodeExporter]

Feature request:

Allow files with plaintext content to be rendered in the viewer (as 
plaintext).

Examples of such content:

*.txt files under scenes/
*.texword files under 
texts/Base/texture_library/loading_screens/City_Zones/

At present, these files can be extracted to external files, but cannot be 
displayed at all within the viewer.

Original issue reported on code.google.com by [email protected] on 11 Sep 2009 at 5:10