Unnecessary pain points in the mesh uploader

[Beq Janus]

In time I revisit the uploader. those messages aren't from Firestorm, they are the mesh asset validation errors sent back from the server. They are put in the log because at present there is no simple route back to the mesh upload dialogue from the arbitrary callback that is triggered. It is not impossible to plumb them in but I've not looked into it. Ideally it could be something that @Vir Linden could sweep into the changes they are making. My reorganisation of the mesh uploader with the resizeable preview paves the way for more verbose messages there is space on the left if needed to place a scrollable widget with all the validation failures. I'm wary too though of making the uploader easier to abuse with poorly constructed mesh, every change we make should steer us towards fostering a better creation culture.