Armature "Envelope" editing.

For defining the deformation distances of Bones, three values are being
used now. The bone tip and root radius define the bone-shape itself and the
"dist" defines the soft area around it. A full (user) doc is in CMS here;

http://www.blender3d.org/cms/Armature_Envelopes.647.0.html

Note: todo still is allowing both Vertex Deform Groups and these Envelopes
together (and or per Bone).

Also part of this commit is:

- New: Hiding bones in EditMode. This is a separate 'hide flag', so you can
  keep the PoseMode hidden Bones separate from EditMode.
  (In the future we should do some kind of bone-grouping or so)
- While transform(), the hotkeys G,R,S only switch mode when the previous
  mode was compatible. Caused conflicts with Crease/BoneDist/etc.
- Deleting the last VertexGroup now also deletes the entire Mesh 'dvert'
  data. Sounds logical, but remember that VertexGroups are partial on a
  Mesh, partial on Object. Weird design decision though...
  Anyhoo, at this moment the only way to have Bone Envelopes deform, is
  by deleting all VertexGroups!
- In PoseMode, the hotkey ALT+S now does both B-Bone size or Envelope,
  depending draw type.
- In EditMode, Extrude now also works when only Root points were selected.
- Weight editing is also symmetrical btw, with the "X-axis Mirror" option
  set.

source/blender/src/transform_generics.c

@@ -127,12 +127,16 @@ static void transform_armature_mirror_update(void)
 					eboflip->tail[0]= -ebo->tail[0];
 					eboflip->tail[1]= ebo->tail[1];
 					eboflip->tail[2]= ebo->tail[2];
+					eboflip->rad_tail= ebo->rad_tail;
 				}
 				if(ebo->flag & BONE_ROOTSEL) {
 					eboflip->head[0]= -ebo->head[0];
 					eboflip->head[1]= ebo->head[1];
 					eboflip->head[2]= ebo->head[2];
+					eboflip->rad_head= ebo->rad_head;
 				}
+				if(ebo->flag & BONE_SELECTED)
+					eboflip->dist= ebo->dist;
 			}
 		}
 	}
@@ -176,6 +180,17 @@ void recalcData(TransInfo *t)
 						VECCOPY (ebo->parent->tail, ebo->head);
 					}
 				}
+				
+				if(arm->drawtype==ARM_ENVELOPE) {
+					if(ebo->oldlength==0.0f) {
+						ebo->rad_head= 0.25f*ebo->length;
+						ebo->rad_tail= 0.10f*ebo->length;
+						if(ebo->parent) {
+							if(ebo->rad_head > ebo->parent->rad_tail)
+								ebo->rad_head= ebo->parent->rad_tail;
+						}
+					}
+				}
 			}
 			if(arm->flag & ARM_MIRROR_EDIT) 
 				transform_armature_mirror_update();
@@ -260,9 +275,8 @@ void initTransModeFlags(TransInfo *t, int mode)
 		t->flag |= T_NO_CONSTRAINT;
 		break;
 	case TFM_SHEAR:
-		t->flag |= T_NO_CONSTRAINT;
-		break;
 	case TFM_CREASE:
+	case TFM_BONE_ENVELOPE:
 		t->flag |= T_NO_CONSTRAINT;
 		break;
 	}