Cleanup & goodies for rigging geeks! :)

- PoseMode: Wkey menu, "Flip Left/Right Names". On selected bones, it flips
  the L/R tags in names, and calls the proper code to rename everything
  that's related (constraint targets, bone-childs, etc).
- PoseMode: Shift+S snapmenu: snap cursor to selected now works
- Outliner: select bones now correctly sets 'active' flag for bones,
  updating the UI as well.
  Also made sure you cannot select hidden bones in outliner.
- 3DWindow: in PoseMode/EditMode draws name of active Bone too (with user
  option "Draw active object name" set.
- Added the new Armature/PoseMode options in View3D pulldowns.

Cleanup:

- moved Pose code from editaction.c to poseobject.c
- removed BSE_editaction.h and BSE_editaction_types.h, moved contents of
  it to BIF_editaction.h. One include per C file should be fine. :)
  I know the src/ structure would require more elaborated includes, but
  we don't have that now...

source/blender/src/editconstraint.c

@@ -53,14 +53,13 @@
 #include "BKE_constraint.h"
 #include "BKE_ipo.h"
 
+#include "BIF_editaction.h"
 #include "BIF_editarmature.h"
 #include "BIF_editconstraint.h"
 #include "BIF_interface.h"
 #include "BIF_screen.h"
 #include "BIF_toolbox.h"
 
-#include "BSE_editaction.h"
-
 #include "blendef.h"
 #include "nla.h"