NLA Editor: Added an operator to set preview range based on the extents of selected strips

This brings it more in line with the other anim editors, and makes like a little
bit easier for animators working on games or looping anims.

release/scripts/startup/bl_ui/space_nla.py

@@ -80,6 +80,7 @@ class NLA_MT_view(Menu):
         layout.separator()
         layout.operator("anim.previewrange_set")
         layout.operator("anim.previewrange_clear")
+        layout.operator("nla.previewrange_clear")
 
         layout.separator()
         layout.operator("nla.view_all")