UI cleanup work;

Proportional edit:

- Proportional mode added to header as button/menu. Including new option
  to have only connected geometry influenced.
- Added icons for proportional & proportional modes
- Make proportional edit data part of Scene, so all gets saved.
  The Global flag G_PROPORTIONAL was removed
- Made sure #defines get used properly, also tweaked order for proportional
  so it starts with regular 'smooth' by default.
- Use ALT+O in editmode to switch to new proportional 'connected' mode

Other UI stuff:

- in EditMode, the layer buttons get hidden... the amount of icons in
  3d header grows to fast. :)
- made less ugly icons for the Manipulators. Still can be better.
- Added alpha-filter for pre-processing Icon-image, giving nicer display
  of icon-antialising on dark or bright backdrops
- disabled Manipulators when in editmode, and current layers don't show
  the edited data.
- Added the value used to define Normal size (editmode draw) in Scene too,
  so it gets saved.

source/blender/include/BIF_transform.h

@@ -58,13 +58,6 @@
 #define CTX_NO_NOR_RECALC	8
 #define CTX_SETLOCALCONST	16
 
-/* TRANSFORM PROPORTIONAL FALLOFF MODES */
-#define PROP_SHARP		0
-#define PROP_LIN		1
-#define PROP_ROOT		2
-#define PROP_SPHERE		3
-#define PROP_CONST		4
-#define PROP_SMOOTH		5
 
 void Transform(int mode, int context);