Fix T39563: Tiny unit-display problem in constraint panels.

There is no good solution here, since RNA props can only have one type/unit.
Tried to find the less worse one - have different RNA props for same DNA value
(a bit like the angle/length for camera lens).

Also fixed two other issues with Transform conctraint:
* Angle were still in degrees (yes, another backward-compatibility breacking).
* Scale was absolute, unlike loc/rot.

Also cleaned up a bit the code, replaced some magic numbers by proper enums, ...

source/blender/blenkernel/BKE_blender.h

@@ -42,7 +42,7 @@ extern "C" {
  * and keep comment above the defines.
  * Use STRINGIFY() rather than defining with quotes */
 #define BLENDER_VERSION         270
-#define BLENDER_SUBVERSION      0
+#define BLENDER_SUBVERSION      1
 /* 262 was the last editmesh release but it has compatibility code for bmesh data */
 #define BLENDER_MINVERSION      262
 #define BLENDER_MINSUBVERSION   0