Adding "Preferences" -> "Other" -> "Brush" tab. This now has

Adding "Preferences" -> "Other" -> "Brush" tab.  This now has
"Default texture scale:".  (Preferences are game specific by the way.)
The default value for this preference is specific to a game, but most
of the time it's 0.5.  This field allows the user to override that default.
This is a feature that was specifically requrested by someone who wants to
try using ZeroRadiant (he wants to set it to 0.25 for his "premium" maps).
It's already a feature in NetRadiant.

git-svn-id: https://zerowing.idsoftware.com/svn/radiant/GtkRadiant/trunk@436 8a3a26a2-13c4-0310-b231-cf6edde360e5