fixed ETag handling in createAvatar
fixed ETag handling in createAvatar

recent versions of chrjs attach an ETag if available; here
defaultSiteIcon's ETag must be removed before PUTing it as new SiteIcon

FND/tiddlyspace,TiddlySpace/tiddlyspace,TiddlySpace/tiddlyspace,FND/tiddlyspace,TiddlySpace/tiddlyspace,FND/tiddlyspace