Entity inspector tab for LOD settings

[MirceaKitsune]

Wanted to start a discussion here before posting this on the tracker if necessary. We've been discussing LOD hiding for light entities recently, and one of the things I was thinking about is how setting up LOD on func_statics might be easier if DarkRadiant had a dedicated menu for LOD settings, just as it has one for configuring AI parameters for instance. There are quite a few different options to configure so it doesn't seem like a bad idea to have a tab for setting them up together in the GUI, where you have buttons and selectors for picking the different models and values... this would help with not having to remember each spawnarg or having to write some model paths by hand without a browser. What do you think?

Looking at the LOD wiki page these are some of the spawnargs I'd propose having in such a tab with an entity selected:

dist_check_period
hide_distance
lod_fadein_range
lod_fadeout_range
lod_#_distance
model_lod_#
skin_lod_#
offset_lod_#
noshadows_lod_#

For lod_#_* type spawnargs I'd offer two sets in the menu: It's rare for any model to have more than two lod meshes provided, most usually have one if they have even that.