For SH-3086: add functions to refetch all previous textures through HTTP and from cache

indra/newview/app_settings/settings.xml

indra/newview/llfloatertexturefetchdebugger.cpp

indra/newview/llfloatertexturefetchdebugger.h

indra/newview/lltexturefetch.cpp

indra/newview/lltexturefetch.h

indra/newview/llviewertexture.cpp

indra/newview/llviewertexture.h

indra/newview/llviewertexturelist.cpp

indra/newview/llviewertexturelist.h

...w/skins/default/xui/en/floater_texture_fetch_debugger.xml